RISC-V: Remove unnecessary frm restore volatile define_insn

RISC-V: Remove unnecessary frm restore volatile define_insn

After we add the frm register to the global_regs, we may not need to
define_insn that volatile to emit the frm restore insns.  The
cooperatively-managed global register will help to handle this, instead
of emit the volatile define_insn explicitly.

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_emit_frm_mode_set): Refactor
	the frm mode set by removing fsrmsi_restore_volatile.
	* config/riscv/vector-iterators.md (unspecv): Remove as
	unnecessary.
	* config/riscv/vector.md (fsrmsi_restore_volatile): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/float-point-dynamic-frm-49.c: Adjust
	the asm dump check times.
	* gcc.target/riscv/rvv/base/float-point-dynamic-frm-50.c: Ditto.
	* gcc.target/riscv/rvv/base/float-point-dynamic-frm-52.c: Ditto.
	* gcc.target/riscv/rvv/base/float-point-dynamic-frm-74.c: Ditto.
	* gcc.target/riscv/rvv/base/float-point-dynamic-frm-75.c: Ditto.

Signed-off-by: Pan Li <pan2.li@intel.com>