scsi: ufs: do pm qos unvoting before calling scsi_done callback

We shouldn't be accessing scsi command's "request" structure after calling
scsi_done callback but it seems pm qos unvoting code path is accessing
this request structure even after caling the scsi_done callback. Fix this
by releasing the pm qos vote before calling scsi_done.

Change-Id: I5c8dd6ba7f0b619397924d73c1fd6c36fe86ebc1
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>