rs6000: Add clobber and guard for vsx_stxvd2x4_le_const [PR116030]

rs6000: Add clobber and guard for vsx_stxvd2x4_le_const [PR116030]

Previously, vsx_stxvd2x4_le_const_<mode> was introduced for 'split1' pass,
so it is guarded by "can_create_pseudo_p ()".  While it would be possible
to match the pattern of this insn during/after RA, this insn could be
updated to make it work for split pass after RA.

And this insn would not be the best choice if the address has alignment like
"&(-16)", so "!altivec_indexed_or_indirect_operand" is added to guard this insn.

2025-01-13  Jiufu Guo  <guojiufu@linux.ibm.com>

gcc/
	PR target/116030
	* config/rs6000/vsx.md (vsx_stxvd2x4_le_const_<mode>): Add clobber
	and guard with !altivec_indexed_or_indirect_operand.

gcc/testsuite/
	PR target/116030
	* gcc.target/powerpc/pr116030.c: New test.