perf/x86: Export perf_assign_events()

perf/x86: Export perf_assign_events()

export perf_assign_events to allow building perf Intel uncore driver
as module

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1395133004-23205-3-git-send-email-zheng.z.yan@intel.com
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: eranian@google.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>