disp: msm: dsi: update args for mipi_dsi_dcs_set_display_brightness

The upstream MIPI DSC set/get brightness api has been changed,
and now it requires one extra argument which is number of
parameters (bytes) to encode brightness value in.
The MIPI specification states that one parameter shall be sent for
devices that support 8-bit brightness levels. For devices that
support brightness levels wider than 8-bit, two parameters
shall be sent.

Change-Id: I08aabf70207d5b7ab79966a1f12fe18b83c34721
Signed-off-by: Rajeev Nandan <rajeevny@codeaurora.org>