metag: perf: prepare for use by oprofile

To allow our perf_events code to work with oprofile the PERF_TYPE_RAW
event type attribute is implemented, which allows the internal encoding
of events to be used externally (this requires some tweaks so that it
handles invalid event types more gracefully), and perf_pmu_name() is
adjusted to return metag_pmu->name instead of metag_pmu->pmu.name (which
is changed to "meta2").

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Robert Richter <rric@kernel.org>
Cc: oprofile-list@lists.sf.net