tools/testing/selftests/powerpc: Add check for power11 pvr for pmu selfests

Some of the tests depends on pvr value to choose
the event. Example:
- event_alternatives_tests_p10: alternative event depends
  on registered PMU driver which is based on pvr
- generic_events_valid_test varies based on platform
- bhrb_filter_map_test: again its dependent on pmu to
  decide which bhrb filter to use
- reserved_bits_mmcra_sample_elig_mode: randome sampling
  mode reserved bits is also varies based on platform

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Disha Goel <disgoel@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250113075858.45137-2-atrajeev@linux.vnet.ibm.com