x86: Require GPR as previous scratch register in LCP stall peepholes

Require general purpose register as previous scratch register in LCP
stall peepholes.

gcc/

	PR target/125958
	* config/i386/i386-expand.cc (ix86_expand_lcp_stall_peephole):
	Replace !REG_P (dest) with !GENERAL_REG_P (dest).

gcc/testsuite/

	PR target/125958
	* gcc.target/i386/pr125958.c: New test.

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