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.

This issue was previously fixed by a42150bd. But later it again resurfaced
with 831a828a.

Change-Id: Ie35194b1e11ae90ff886b1be22cf02c842a76d1a
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>