scsi: ufs: add option to override the command timeout

Some platforms might be very slow and command completion may take
much longer than default scsi command timeouts.
SCSI Read/Write command timeout can be changed by blk_queue_rq_timeout()
but there is no option to override timeout for rest of the scsi commands.

This change adds device tree parameter "scsi-cmd-timeout" to allow
overriding the default scsi command timeout for all scsi commands.

Change-Id: Ib77d39ebb7787f8d8fa66c6e21a98df8b43103fd
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>