libatomic: Improve cpuid usage in __libat_feat1_init

Check the result of __get_cpuid and process FEAT1_REGISTER only when
__get_cpuid returns success.  Use __cpuid instead of nested __get_cpuid.

libatomic/ChangeLog:

	* config/x86/init.c (__libat_feat1_init): Check the result of
	__get_cpuid and process FEAT1_REGISTER only when __get_cpuid
	returns success.  Use __cpuid instead of nested __get_cpuid.