disp: msm: sde: updating DSI command packet creation for MIPI flags

At present, code is checking only for MSM_REQ_ACK flag which is set for
read commands and ignores all other flag states.
This fix takes all the different states that are configured as the DSI
Command MIPI Flag states and sets it.
Also, added the backlight brightness control support with different DCS
command(0xC2) to update backlight brightness.

Change-Id: I689e902e7d997afcb629084e89e42361bf1c685b
Signed-off-by: Rajesh Bharathwaj <rajeshbharathwaj@codeaurora.org>