PR target/117449: Restrict vector rotate match and split to pre-reload

PR target/117449: Restrict vector rotate match and split to pre-reload

The vector rotate splitter has some logic to deal with post-reload splitting
but not all cases in aarch64_emit_opt_vec_rotate are post-reload-safe.
In particular the ROTATE+XOR expansion for TARGET_SHA3 can create RTL that
can later be simplified to a simple ROTATE post-reload, which would then
match the insn again and try to split it.
So do a clean split pre-reload and avoid going down this path post-reload
by restricting the insn_and_split to can_create_pseudo_p ().

Bootstrapped and tested on aarch64-none-linux.

Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
gcc/

	PR target/117449
	* config/aarch64/aarch64-simd.md (*aarch64_simd_rotate_imm<mode>):
	Match only when can_create_pseudo_p ().
	* config/aarch64/aarch64.cc (aarch64_emit_opt_vec_rotate): Assume
	can_create_pseudo_p ().

gcc/testsuite/

	PR target/117449
	* gcc.c-torture/compile/pr117449.c: New test.