RISC-V: Remove incorrect function gate gather_scatter_valid_offset_mode_p

RISC-V: Remove incorrect function gate gather_scatter_valid_offset_mode_p

Come back to review the codes of gather/scatter, notice gather_scatter_valid_offset_mode_p looks odd.
gather_scatter_valid_offset_mode_p is supposed to block vluxei64/vsuxei64 in RV32 system.
However, it failed to do that since it is passing data_mode instead of index mode:

riscv_vector::gather_scatter_valid_offset_mode_p (<RATIO2:MODE>mode)
It should be RATIO2I instead of RATIO2.
So we have this following iterators which already can block the this situation:

(define_mode_iterator RATIO8I [
  RVVM1QI
  RVVM2HI
  RVVM4SI
  (RVVM8DI "TARGET_VECTOR_ELEN_64 && TARGET_64BIT")
])

We can see TARGET_64BIT to block EEW64 index mode on RV32 system.
So, gather_scatter_valid_offset_mode_p is no longer needed.

After remove it, I find due to incorrect gather_scatter_valid_offset_mode_p.
We failed to vectorize such case in RV32 in the past:

  void __attribute__ ((noinline, noclone))                                     \
  f_##DATA_TYPE (DATA_TYPE *restrict dest, DATA_TYPE *restrict src,            \
		 INDEX##BITS *restrict indices, INDEX##BITS *restrict cond)    \
  {                                                                            \
    for (int i = 0; i < 128; ++i)                                              \
      if (cond[i])                                                             \
	dest[i] += src[indices[i]];                                            \
  }
  T (int64_t, 8)
TEST_ALL (TEST_LOOP)

https://godbolt.org/z/T3ara3fM3

Checked compiler explorer, we can see GCC failed to vectorize it but Clang can vectorize it.

So adapt the tests checking vectorization cases from 8 -> 11.

Confirm we have same behavior as Clang now.

Tested on zvl128/zvl256/zvl512/zvl1024 no regression.

Note this is not an optimization patch, it's buggy codes fix patch.

gcc/ChangeLog:

	* config/riscv/autovec.md
	(mask_len_gather_load<RATIO1:mode><RATIO1:mode>):
	Remove gather_scatter_valid_offset_mode_p.
	(mask_len_gather_load<mode><mode>): Ditto.
	(mask_len_scatter_store<RATIO1:mode><RATIO1:mode>): Ditto.
	(mask_len_scatter_store<mode><mode>): Ditto.
	* config/riscv/predicates.md (const_1_or_8_operand): New predicate.
	(vector_gs_scale_operand_64): Remove.
	* config/riscv/riscv-protos.h (gather_scatter_valid_offset_mode_p): Remove.
	* config/riscv/riscv-v.cc (expand_gather_scatter): Refine code.
	(gather_scatter_valid_offset_mode_p): Remove.
	* config/riscv/vector-iterators.md: Fix iterator bugs.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-1.c: Adapt test.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-10.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-11.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-2.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-3.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-4.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-5.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-6.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-7.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-8.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_gather_load_32-9.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-1.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-10.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-2.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-3.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-4.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-5.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-6.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-7.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-8.c: Ditto.
	* gcc.target/riscv/rvv/autovec/gather-scatter/mask_scatter_store_32-9.c: Ditto.