[PATCH] USB Storage: remove dependency on SCSI-provided serial/tag number

This patch started life as as531 from Alan Stern.  It has been rediffed
against the latest tree.

The SCSI people have deprecated the use of scsi_cmnd.serial_number for
anything other than printk.  Worse than that, the SCSI core doesn't
always increment the number (when the error handler is running, for
example).  So this patch creates a locally-stored value for use in
bulk-only tags.  The net result is a simplification, since we no longer
have to save & restore the serial_number value while autosensing.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>