[ARM] Use __ARM_ARCH and __ARM_FEATURE_LDREX instead of __ARM_ARCH__

2018-06-21  Christophe Lyon  <christophe.lyon@linaro.org>

	libatomic/
	* config/arm/arm-config.h (__ARM_ARCH__): Remove definitions, use
	__ARM_ARCH instead. Use __ARM_FEATURE_LDREX to define HAVE_STREX
	and HAVE_STREXBHD

	libgcc/
	* config/arm/lib1funcs.S (__ARM_ARCH__): Remove definitions, use
	__ARM_ARCH and __ARM_FEATURE_CLZ instead.
	(HAVE_ARM_CLZ): Remove definition, use __ARM_FEATURE_CLZ instead.
	* config/arm/ieee754-df.S: Use __ARM_FEATURE_CLZ instead of
	__ARM_ARCH__.
	* config/arm/ieee754-sf.S: Likewise.
	* config/arm/libunwind.S: Use __ARM_ARCH instead of __ARM_ARCH__.

From-SVN: r261841