video: msm: Increase MDP clock multiplier

 * The porch values used on Samsung's panel drivers are very tight, and
   cause the MDP clock rate calculation to be right on the edge of
   stability. Underrun was occurring when FLIP_LR was set on any pipe,
   which is the case for 180 rotation (FLIP_LR|FLIP_UD).
 * Raise the multiplier from 1.15 to 2 to fix the underrun.

Change-Id: Iadd7facde88520a90a4394f57fe28214a92741a3