scsi: ufs: make sure all interrupts are processed

As multiple requests are submitted to the ufs host controller in
parallel there could be instances where the command completion
interrupt arrives later for a request that is already processed
earlier as the corresponding doorbell was cleared when handling
the previous interrupt. Read the interrupt status in a loop after
processing the received interrupt to catch such interrupts and
handle it.

Change-Id: I91c1ba3360592f258a2c3c4e902394c3ddc77bca
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>