Revert qualcomm's contributions on mutex.h

Related commit is 3f2bc4d6eb5.

Change-Id: Ia92b90b44bf92b7e40ec984e428379ee1a6c047b
Signed-off-by: Iliyan Malchev <malchev@google.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>