The valid mask for both offcore_response_0 and
offcore_response_1 was wrong for SNB/SNB-EP,
IVB/IVB-EP. It was possible to write to
reserved bit and cause a GP fault crashing
the kernel.
This patch fixes the problem by correctly marking the
reserved bits in the valid mask for all the processors
mentioned above.
A distinction between desktop and server parts is introduced
because bits 24-30 are only available on the server parts.
This version of the patch is just a rebase to perf/urgent tree
and should apply to older kernels as well.