msm: mdss: use the dsi panel API for sending init commands

The dsi panel driver implements the dsi command send
and receive functions.  However, on 8x10, it was using
its own version.  This change is to use the functions
defined in the panel driver.

Change-Id: I4dcec67fecb51f02b65ee7818ccbe7729f3e6831
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>