MIPS: perf: Change the "mips_perf_event" table unsupported indicator.

MIPS: perf: Change the "mips_perf_event" table unsupported indicator.

Change the indicator from 0xffffffff in the "event_id" member to
zero in the "cntr_mask" member. This removes the need to initialize
entries that are unsupported. This also solves a problem where the
number of entries in the table was increased based on a globel enum
used for all platforms, but the new unsupported entries were not added
for mips. This was leaving new table entries of all zeros that we not
marked UNSUPPORTED.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/4110/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>