msm: mdss: cleanup auto-refresh implementation

Auto-refresh is used on smart displays to refresh display without
SW intervention, similar to dumb displays. So when it is on, display
controller will automatically send new frame every time panel TE signal
is received. Now as per the HW implementation, disabling auto-refresh
requires that display controller is idle and there is no frame transfer
on-going. To achieve this, we need to follow certain disable sequence.
To implement this disable sequence, clean up current implementation and
introduce auto-refresh state machine.

Change-Id: Iac5d76b6431f7ef2fcd68114e19c5cb5fb02577d
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>