scsi: ufs: remove unwanted checks from hibern8 sequence

We are unnecessarily checking for the request/task doorbell status
during hibern8 enter/exit path but it's very important to have the
minimal latencies for hibern8 enter/exit in order to achieve agressive
power management strategies for UFS. So these unecessary checks are moved
out of this hot path.

Change-Id: Ibaeddca7bd516d71eb03b02a1fc1a86f05038f08
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>