mdss: display: add rotator interface to mdss driver

Add rotator session management support with overlay interface using MDP
flag MDSS_MDP_ROT_ONLY. Overlay interface can only support overlay
surface or rotator (written back to memory) but not both.

Change-Id: Ib2f494683b2e6c2fd8c67818df2b57afb82a3df3
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>