UAS: Free status URB when we can't find the SCSI tag.

In the UAS status URB completion handler, we need to free the URB, no
matter what happens.  Fix a bug where we would leak the URB (and its
buffer) if we couldn't find a SCSI command that is associated with this
status phase.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>