x86, uv: Enable Westmere support on SGI UV

Enable Westmere support on SGI UV.  The UV initialization code is dependent on
the APICID bits.  Westmere-EX uses different APIC bit mapping than Nehalem-EX.
This code reads the apic shift value from a UV MMR to do the proper bit
decoding to determint the pnode.

Signed-off-by: Russ Anderson <rja@sgi.com>
LKML-Reference: <20101026212728.GB15071@sgi.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>