selftests/powerpc/pmu: Add selftest for group constraint check MMCRA sample bits

Events with different "sample" field values which is used to program
Monitor Mode Control Register A (MMCRA) in a group will fail to
schedule. Testcase uses event with load only sampling mode as group
leader and event with store only sampling as sibling event. So that it
can check that using different sample bits in event code will fail in
event open for group of events

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/20220610134113.62991-23-atrajeev@linux.vnet.ibm.com