msm: mdss: add support for multi-rect feature

Add support for DMA multirect pipes available in new MDP revision.
These pipes are able to fetch two different buffers and rectangles to
allow more layers to be fetched. Add support and proper validation
checks for limitations.

CRs-Fixed: 987777
Change-Id: I588ecd7829a45908241f6d9fa1e97147e79798f6
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>