msm: mdss: set dsi clock lane to proper state on 8939

For 8939, dsi clock lane may get stuck at hs mode. It
needs manual control of clock lane to avoid it.
Force clock lane to HS mode before kick off and clear
it after completion.

Change-Id: I8182489d2d5eaf041b4869af71155378dd3aea99
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>