scsi: ufs: add some custom testbus register reads for debugging purpose

Add some useful testbus register reads. It is helpful to capture testbus
regs to debug specific UFS issues.

Change-Id: I2ce741eb767c97059aae3f21f6ca8492c8ffa00f
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>