FROMGIT: scsi: ufs: Set the CP flag for RT requests

Make the UFS device execute realtime (RT) requests before other requests.
This will be used in Android to reduce the I/O latency of the foreground
app.

Change-Id: Ia8fa42517e6f8e11439bd91b2e23762c00845724
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
(cherry picked from commit 00d2fa28 git://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git

 for-next)
Signed-off-by: Bart Van Assche <bvanassche@google.com>