selftests/powerpc/pmu: Add macros to parse event codes

Each platform has raw event encoding format which specifies the bit
positions for different fields. The fields from event code gets
translated into performance monitoring mode control register (MMCRx)
settings. Patch add macros to extract individual fields from the event
code.

Add functions for sanity checks, since testcases currently are only
supported in power9 and power10.

Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
[mpe: Read PVR directly rather than using /proc/cpuinfo]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220127072012.662451-4-kjain@linux.ibm.com