rs6000: Fix split of ashdi3_extswsli_dot for memory (PR71670)

rs6000: Fix split of ashdi3_extswsli_dot for memory (PR71670)

The splitter for ashdi3_extswsli_dot for cr0 with memory uses emit_insn
gen_ashdi3_extswsli_dot, which does not work because that emits a scratch,
while the splitter runs after reload so there should be a real register
instead.  We can laboriously fix that up, or emit using
gen_ashdi3_extswsli_dot2 instead.  This patch does the latter.

	PR target/71670
	* config/rs6000/rs6000.md (ashdi3_extswsli_dot): Use
	gen_ashdi3_extswsli_dot2 instead of gen_ashdi3_extswsli_dot.

gcc/testsuite/
	PR target/71670
	* gcc.target/powerpc/pr71670.c: New testcase.

From-SVN: r237813