ACPICA: Mutex support: Fix release ordering issue and current sync level

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=471

Signed-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>