perf event: Prevent unbound event__name array access

event__name[] is missing an entry for PERF_RECORD_FINISHED_ROUND, but we
happily access the array from the dump code.

Make event__name[] static and provide an accessor function, fix up all
callers and add the missing string.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ian Munsie <imunsie@au1.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20101207124550.432593943@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>