aarch64: Fix aarch64_split_imm24 patterns

aarch64: Fix aarch64_split_imm24 patterns

Both patterns used !reload_completed as a condition, which is
questionable at best.  The branch pattern failed to include a
clobber of CC_REGNUM.  Both problems were unlikely to trigger
in practice, due to how the optimization pipeline is organized,
but let's fix them anyway.

gcc:
	* config/aarch64/aarch64.cc (aarch64_gen_compare_split_imm24): New.
	* config/aarch64/aarch64-protos.h: Update.
	* config/aarch64/aarch64.md (*aarch64_bcond_wide_imm<GPI>): Use it.
	Add match_scratch and cc clobbers.  Use match_operator instead of
	iterator expansion.
	(*compare_cstore<GPI>_insn): Likewise.