scsi: ufs: clear fields UTRD, UPIU req and rsp before new transfers

Some of the data structures (like response UPIU) and/or its elements
(unused fields) should be cleared before sending out the respective
command to UFS device.

This change clears the UPIU response data structure for query commands
and NOP command before sending out the command. We also initialize the
PRDT table length to zero which should take care of commands which doesn't
have any data associated with it. We are also clearing the unused fields in
request UPIU for NOP command.

Change-Id: Iac02618cd5e9d97883652e134c5365884f3d0b44
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>