scsi: ufs: fix bugs related to null pointer access and array size

In this change there are a few fixes of possible NULL pointer access
and possible access to index that exceeds array boundaries.

Change-Id: I4a2dbc417d53931e012925978cd52e3397356ec2
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>
[subhashj@codeaurora.org: resolved trivial merge conflicts]
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>