x86: Inline strncmp only with -minline-all-stringops

x86: Inline strncmp only with -minline-all-stringops

Expand strncmp to "repz cmpsb" only with -minline-all-stringops since
"repz cmpsb" can be much slower than strncmp function implemented with
vector instructions, see

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43052

gcc/

	PR target/95458
	* config/i386/i386-expand.c (ix86_expand_cmpstrn_or_cmpmem):
	Return false for -mno-inline-all-stringops.

gcc/testsuite/

	PR target/95458
	* gcc.target/i386/pr95458-1.c: New test.
	* gcc.target/i386/pr95458-2.c: Likewise.