x86, amd: Extract compute unit information for AMD CPUs

Get compute unit information from CPUID Fn8000_001E_EBX.
(See AMD CPUID Specification - publication # 25481, revision 2.34,
September 2010.)

Note that each core on a compute unit still has a core_id of its own.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
LKML-Reference: <20100930123857.GE20545@loge.amd.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>