msm: mdss: send dsi data and command independently

Send dsi pixel data and dcs commands independent of
each other. On 8939 DSI controller supports burst mode,
so we don't need to wait for dcs commands to finish before
sending display pixel data in case burst mode is enabled.

Change-Id: I5777a72b8ad84a7929aa6e06849060efdebb0d7b
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>
Signed-off-by: Bharat Pawar <bpawar@codeaurora.org>