uas: fix deadlocky memory allocations

There are also two allocations with GFP_KERNEL in the pre-/post_reset
code paths. That is no good because that is a part of the SCSI error handler.

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>