msm: mdss: release all overlay resources on last fb release

There are cases where the last frame buffer reference is released from a
different pid than the one who originally allocated the resource.
In these cases we can still deallocate all resources currently allocated
as we know that all references on fb dev have been released.

Change-Id: Ice2ca8df765cb8c4537a89fec887cb125d820d7a
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>