mdss: display: Add Mobile Display SubSystem driver

- Implements Linux frame buffer interface to interact with userspace
  libraries and applications, based on msm_fb frame buffer.
- Implement MDP driver which handles MDP core data path setup and
  hardware blocks programming.
- Support for UI through Linux frame buffer FBIOPAN_DISPLAY ioctl.

Change-Id: Ib98677b8d81d74283b27dea08a9f1a705c101bce
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>