msm_fb: display: allocate mdp writeback memory

The writeback buffer is already reserved on the board side. This
allocation separate writeback buffer from framebuffer.

Change-Id: I312be3e0dfcf4c5b611cd06cd68d2baae7e2add8
Signed-off-by: Huaibin Yang <huaibiny@codeaurora.org>
6 files changed