ring-buffer: Force rb_end_commit() and rb_set_commit_to_write() inline

Both rb_end_commit() and rb_set_commit_to_write() are in the fast path of
the ring buffer recording. Make sure they are always inlined.

Link: http://lkml.kernel.org/r/20161121183700.GW26852@two.firstfloor.org



Reported-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>