scsi: ufs-qcom: Add check for ufs bootdevice

On qcom platforms, bootdevice is the primary storage
device. The regulators to this device are left ON by
the bootloaders. Detecting further in the init sequence
that UFS is not the bootdevice entails turning-off of
these regulators without sending PON. This is bad for
the underlying storage device.

Change-Id: I7e9231f0bcf90d8f329146ae2d831bbb5ef8190e
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>