Fixes a problem where if multiple mutexes of the same sync level
are acquired but then not released in strict opposite order, the
current sync level becomes confused and can cause errors.
ACPICA BZ 471.

http://acpica.org/bugzilla/show_bug.cgi?id=471Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>