msm: mdss: Add default dither programming from CTL init

The ability to program default values to the dither hardware
is broken using the new post-processing versioning framework.
This change adds back the functionality of programming the
dither block based on panel bits per pixel.

Change-Id: I016e7ebec3e05107e677d6ca6e2ef7fd078af048
Signed-off-by: Benet Clark <benetc@codeaurora.org>