Fix GAS testsuite failures for COFF/PE based ARM targets.

	PR gas/19276
gas	* config/tc-arm.h (SUB_SEGMENT_ALIGN): Do not define for COFF/PE
	targets.

testsuite	* gas/arm/align64.d: Skip for COFF/PE targets.
	* gas/arm/bundle-lock.d: Adjust for COFF/PE targets.