drm/msm/sde: use atomic counter for pending frame done

SDE encoder uses bit mask logic to check the pending
pp_done IRQ for dual dsi and trigger release fence
when both IRQs are received. It causes issue when
encoder triggers two frames back to back without
waiting for first frame done. Bitmask clears the
frame done prematurely and miss to trigger the release
fence for second frame. Atomic counter usages allows
to track the number of pending IRQ and release
frame_done when both pp_done IRQs are received.

Change-Id: I669aea124bae922641afe5d34f8f035dc5de82b3
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>
Signed-off-by: Bruce Hoo <bingchua@codeaurora.org>
Signed-off-by: Ray Zhang <rayz@codeaurora.org>