UAS: Re-add workqueue items if submission fails.

UAS: Re-add workqueue items if submission fails.

BugLink: http://bugs.launchpad.net/bugs/901215

If the original submission (or allocation) of the URBs for a SCSI
command fails, the UAS driver sticks the command structure in a
workqueue and schedules uas_do_work() to run.  That function removes the
entire queue before walking across it and attempting to resubmit.

Unfortunately, if the second submission fails, we will leak memory
(because an allocated URB was not submitted) and possibly leave the SCSI
command partially enqueued on some of the stream rings.  Fix this by
checking whether the second submission failed and re-queueing the
command to the UAS workqueue and scheduling it.

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>
(cherry picked from commit ea9da1c79eb9a28176550d0b8ba9166e6e5f42b8)

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Herton Krzesinski <herton.krzesinski@canonical.com>