msm: mdss: fix rotator session not being closed correctly

User space expects non-negative number as session id, update rotator
mask to avoid making rotator session as negative.
When rotator is closed, need to recalculate bus/mdp clock numbers.

Change-Id: I6c0e3bfa5394fb64b78fb47be1f24462e320916d
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>