selftests/powerpc/pmu: Add selftest for group constraint check for PMC5 and PMC6

Events using Performance Monitor Counter 5 (PMC5) and Performance
Monitor Counter 6 (PMC6) can't have other fields in event code like
cache bits, thresholding or marked bit. PMC5 and PMC6 only supports base
events: ie 500fa and 600f4. Other combinations should fail. Testcase
tries setting other bits in event code for 500fa and 600f4 to check this
scenario.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220610134113.62991-17-atrajeev@linux.vnet.ibm.com