ARM: dts: msm: add dispcc clock reference for dsi-display nodes

Currently the dsi clock handles are under the dsi
controller DT node. As soon as the controller probe
finishes, the dispcc sync state can get called before
the dsi_display probe potentially disturbing the clock
votes for cont_splash use case. dsi_display adds its
component to the list of components hence controlling the
bind which adds the dsi clock votes. There is no separate
component for the dsi_ctrl. Hence we are no longer
protected by the component model in this case against the
disp cc sync state getting triggered after the dsi_ctrl
probe. To protect against this incorrect sync state trigger
add a dummy MDP clk vote handle to the dsi_display
DT node. Since the dsi_display driver does not parse
MDP clock nodes, no actual vote shall be added and this
change is done just to satisfy sync state requirements.

Change-Id: I47c458f4f6f2937effdd1212496b41eacab4e052