drm/msm/mdp5: Use the newly introduced enum mdp_component_type

When calculating phase steps, let's use the same enum
mdp_component_type in order to ease the readability; 0/1 indexes
are a bit confusing and we now have explicit values to index
this type of arrays.

Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>