mdss: display: Fix clock disable/unprepare calls for split display

For split display, the clock disable calls for DSI clocks
for both the controllers should happen before
calling clock unprepare APIs. Implement this sequence
when broadcast mode is enabled.

Change-Id: Ifb7436bc88e9b5c71623775815052c15dcc42844
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>