scsi: ufs: sysfs: device descriptor

This patch introduces a sysfs group entry for the UFS device descriptor
parameters. The group adds "device_descriptor" folder under the UFS driver
sysfs entry (/sys/bus/platform/drivers/ufshcd/*). The parameters are shown
as hexadecimal numbers. The full information about the parameters could be
found at UFS specifications 2.1.

Signed-off-by: Stanislav Nijnikov <stanislav.nijnikov@wdc.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>