msm: mdss: refactor the rotation logic

Creating a rotation session manager to manage the rotation sessions.
At creation time, rotation object is not assigned to the underlying
hardware resources (i.e. pipe, mixer, controller, and write-back).
The hardware assignment happens only at the time of commit, and released
after the commit is done.

Change-Id: I33bf625a177362953c11eefc2a779a5af409964b
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>