msm: mdss: refactor mdss color formats

Add missing color formats and reorganize color formats to have better
code reuse and make it easy to add new formats if required.

Change-Id: Ic7c6bb6f35a9c282d9ef99bd5e1d18b0b8033971
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>