msm: mdss: update the DSI h/w revision based checks for msm8937

The step version is different between msm8996 and msm8937 even
though the major/minor versions are the same. Update the DSI PHY
and clamp register programming for msm8937 by checking for the
step version to avoid incorrect DSI register programming.

Change-Id: Ia9582b2779f40429586e8709bb73c9a5c79bd6c5
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>