perf test: Check counts on all cpus in test__open_syscall_event_on_all_cpus

perf test: Check counts on all cpus in test__open_syscall_event_on_all_cpus

We were bailing out after the first count mismatch, do it in all to see
if only some CPUs are not getting the expected number of events.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>