msm: mdss: use the common dsi utility api

There are two separate dsi host controller drivers currently.
While the h/w specific operations are different, the dsi
command utility functions can be shared as that is purely s/w.
This change is to use the common dsi command utility api.

Change-Id: I381eb6dee80a88e0d4ea17a18fa030df7d13db8c
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>