msm: mdss: read DSI CTRL and PHY revision properly

In the current implementation DSI PHY revision is read once
DSI PHY initialization is complete. But this needs to be done
before initializing PHY, so that correct PHY initialization
sequence can be executed.

Change-Id: I6f0cd59d63d0a8c0a5d47284f2e86e72f37d099f
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>