msm: mdss: Define AD BL linearity LUT size independent of maximum BL value

Previously the AD BL linearity LUT size was dependent on the maximum BL
value for the hardware. Now it has been defined to a fixed value so that
the LUT is consistent across hardwares.

Change-Id: I11cc2f135118cf3f63fdeca820f4c8430f9d127d
Signed-off-by: Benet Clark <benetc@codeaurora.org>