scsi: ufs: avoid spurious UFS host controller interrupts

When control reaches to Linux UFS driver during UFS boot mode, UFS host
controller interrupt status/enable registers may have left over settings.
In order to avoid any spurious interrupts due to these left overs, it's
important to clear these interrupt status/enable registers before enabling
UFS interrupt handling.

CRs-Fixed: 709250
Change-Id: Ibb554ca6e1bd2f69663a741f15948f80c52ce75c
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>