msm_fb: Display: Fix Dithering issue for rgb565 format

Using RGB888 as source format and rgb565 as destination pixel format,
will cause image corruption on the display. Fix this issue by
setting the destination format as RGB888 in MDP and DSI controller
pixel format as RGB565 for DSI specific panels.

CRs-Fixed: 377484
Change-Id: If58976ee9cd4825efb39437170e54796fa2213e0
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>