mips: cacheinfo: report shared CPU map

Report L1 caches as shared per core; L2 - per cluster.

This fixes "perf" that went crazy if shared_cpu_map attribute not
reported on sysfs, in form of

/sys/devices/system/cpu/cpu*/cache/index*/shared_cpu_list
/sys/devices/system/cpu/cpu*/cache/index*/shared_cpu_map

Signed-off-by: Vladimir Kondratiev <vladimir.kondratiev@intel.com>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org