perf stat: Define MATCH_EVENT for easy attr checking

MATCH_EVENT is useful:

 1. for multiple attrs checking
 2. avoid repetition of PERF_TYPE_ and PERF_COUNT_ and save space
 3. avoids line breakage

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1246440909.3403.5.camel@hpdv5.satnam>
Signed-off-by: Ingo Molnar <mingo@elte.hu>