msm: fb: add support to set the output format

Add support to set the output of the interface based on the
grayscale value. The grayscale value must be set to a format
specified according to the V4L2 FOURCC pixel format definitions.
We translate from the FOURCC pixel format to the corresponding
MDP format when setting the final output format. For example,
this is used to set the output format to YUV420 for HDMI TVs
that are HDMI 2.0 compliant.

Change-Id: Id5623f1211b743b54002c22b19d81dbd13e6564f
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>