x86: Don't inline memmove for -Os

Update ix86_expand_movmem to return false if optimize_function_for_size_p
returns true to avoid inlining memmove for -Os.

gcc/

	PR target/125355
	* config/i386/i386-expand.cc (ix86_expand_movmem): Return false
	for -Os.

gcc/testsuite/

	PR target/125355
	* gcc.target/i386/pr125355.c: New test.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>