drm/msm/mdp5: Add pingpong entry to mdp5 config table

Pingpong register base addresses are different across platforms.
This change adds this information to config table and initialize
the values for 8x74 and 8084.

Signed-off-by: Hai Li <hali@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>