msmfb: mdss: framework update to support other MDP cores

Make the mdss_fb generic so other MDP cores can share the code.
Move overlay and other functions which are specific to MDP5 hardware
to separate files so that mdss_fb can maintain common framebuffer dev
API for different display hardware.

Change-Id: Ic7dc631f5bdf2471719df785456887627a6d2c60
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>
8 files changed