Check FMA after COMMON_CPUID_INDEX_80000001

Since the FMA4 bit is in COMMON_CPUID_INDEX_80000001 and FMA4 requires
AVX, determine if FMA4 is usable after COMMON_CPUID_INDEX_80000001 is
available and if AVX is usable.

	[BZ #20195]
	* sysdeps/x86/cpu-features.c (get_common_indeces): Move FMA4
	check to ...
	(init_cpu_features): Here.