scsi: ufs: add support to read device and string descriptors

This change adds support to read device descriptor and string descriptor
from a UFS device

Reviewed-by: Gilad Broner <gbroner@codeaurora.org>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Raviv Shvili <rshvili@codeaurora.org>
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>