scsi: ufs: reduce the interrupts for power mode change requests

DME commands such as Hibern8 enter/exit and gear switch generate 2
completion interrupts, one for confirmation that command is received by
local UniPro and 2nd one is the final confirmation after communication
with remote UniPro. Currently both of these completions are registered
as interrupt events which is not quite necessary and instead we can just
wait for the interrupt of 2nd completion, this should reduce the number
of interrupts and could reduce the unnecessary CPU wakeups to handle
extra interrupts.

Reviewed-by: Gilad Broner <gbroner@codeaurora.org>
Reviewed-by: Dolev Raviv <draviv@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>