Update family and model detection for AMD CPUs

AMD CPUs uses the similar encoding scheme for extended family and model
as Intel CPUs as shown in:

http://support.amd.com/TechDocs/25481.pdf

This patch updates get_common_indeces to get family and model for both
Intel and AMD CPUs when family == 0x0f.

	[BZ #19214]
	* sysdeps/x86/cpu-features.c (get_common_indeces): Add an
	argument to return extended model.  Update family and model
	with extended family and model when family == 0x0f.
	(init_cpu_features): Updated.