powerpc/perf: Add hv_gpci interface header
powerpc/perf: Add hv_gpci interface header

"H_GetPerformanceCounterInfo" (refered to as hv_gpci or just gpci from
here on) is an interface to retrieve specific performance counters and
other data from the hypervisor. All outputs have a fixed format. This
header only describes the portions of the interface that we plan on
using in linux at this time.

Signed-off-by: Cody P Schafer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <864f124608374e06e4da1fa5d2e47ed839b95411@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs