selftests/powerpc/pmu: Add interface test for bhrb disable field for non-branch samples

The testcase uses "instructions" event to generate the samples and fetch
Monitor Mode Control Register A (MMCRA) when overflow. Branch History
Rolling Buffer(bhrb) disable bit is part of MMCRA which need to be
verified by perf interface. Incase sample is not of branch type, bhrb
disable bit is explicitly set to 1. Testcase checks if the bhrb disable
bit is set of MMCRA register via perf interface for ISA v3.1 platform

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220610134113.62991-15-atrajeev@linux.vnet.ibm.com