[PATCH][AArch64] Fix generation of tst (PR87763)

[PATCH][AArch64] Fix generation of tst (PR87763)

The TST instruction no longer matches in all cases due to changes in
Combine.  The fix is simple, we now need to allow a subreg as well when
selecting the cc_mode.  This fixes the tst_5.c and tst_6.c failures.

AArch64 regress & bootstrap OK.

	PR rtl-optimization/87763
	* config/aarch64/aarch64.c (aarch64_select_cc_mode):
	Allow SUBREG when matching CC_NZmode compare.

From-SVN: r268265