scsi: ufs: update device descriptor maximum size

According to JESD220B - UFS v2.0, the maximum size of device descriptor
has changed from 0x1F to 0x40. This patch updates the maximum size of
this descriptor.

Change-Id: I5f5de516a2d86e1f4409e44e1b2db62a624207b9
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>