perf_counter: use misc field to widen type

Push the PERF_EVENT_COUNTER_OVERFLOW bit into the misc field so that
we can have the full 32bit for PERF_RECORD_ bits.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090408130408.891867663@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>