scsi: ufs: change clock gating timeout to 50ms

Clock gating timeout is generally choosen such a way that it doesn't
impact storage benchmark performance numbers. Although current timeout
value of 150ms seems high hence this change reduces it to 50ms to save
power clock gating timeout. Reducing it to 50ms doesn't affect the
storage performance benchmark numbers.

Change-Id: Ia131fc420995f44d8446f3800c19de40fedea504
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>