perf: Update the mmap control page on mmap()

Apparently we didn't update the mmap control page right after mmap(),
which leads to surprises when userspace wants to use it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Arun Sharma <asharma@fb.com>
Link: http://lkml.kernel.org/n/tip-dcpi7164djsexmx6ya7lilrc@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --cc kernel/events/core.c
Simple merge