Ignore SyncLevel for methods that have been auto-serialized.

Cannot use a SyncLevel for methods that have been serialized at load-time
or runtime because this may interfere with any existing use of SyncLevels
within the ASL code. So, we simply ignore the SyncLevel for these methods,
thus preserving any existing SyncLevel priorities. Note, the use of
SyncLevels is actually rather rare within BIOS ASL code.