powerpc/perf: Cleanup cache_sel bits comment

Update the raw event code comment in power9-pmu.c with respect to
"cache" bits, since power9 MMCRC does not support these.

Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
1 file changed