ARM: Fix conditional execution [PR113915]

ARM: Fix conditional execution [PR113915]

By default most patterns can be conditionalized on Arm targets.  However
Thumb-2 predication requires the "predicable" attribute be explicitly
set to "yes".  Most patterns are shared between Arm and Thumb(-2) and are
marked with "predicable".  Given this sharing, it does not make sense to
use a different default for Arm.  So only consider conditional execution
of instructions that have the predicable attribute set to yes.  This ensures
that patterns not explicitly marked as such are never conditionally executed.

gcc/ChangeLog:
	PR target/113915
	* config/arm/arm.md (NOCOND): Improve comment.
	(arm_rev*) Add predicable.
	* config/arm/arm.cc (arm_final_prescan_insn): Add check for
	PREDICABLE_YES.

gcc/testsuite/ChangeLog:
	PR target/113915
	* gcc.target/arm/builtin-bswap-1.c: Fix test to allow conditional
	execution both for Arm and Thumb-2.