powerpc/perf: Fix handling of L3 events with bank == 1

powerpc/perf: Fix handling of L3 events with bank == 1

Currently we reject events which have the L3 bank == 1, such as
0x000084918F, because the cache field is non-zero.

However that is incorrect, because although the bank is non-zero, the
value we would write into MMCRC is zero, and so we can count the event.

So fix the check to ignore the bank selector when checking whether the
cache selector is non-zero.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>