msm: mdss: update the wait sequence for DSI_VIDEO_DONE interrupt

At present, the previous VIDEO_DONE interrupt bit is cleared and
the VIDEO_DONE_MASK bit are set in the DSI interrupt register by a
single register write operation. This seems to be not reliable
always and the DSI_VIDEO_DONE interrupt is generated for the
previous VIDEO_DONE sometimes. Fix this sequence by clearing the
previous DSI_VIDEO_DONE interrupt bit first followed by a separate
register write to enable the VIDEO_DONE_MASK bit.

Change-Id: Ic51424031bb1e4b5c5fae21bfe180c4620151c21
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>