mdss: Display: Add bus clocks to be part of DSI clock control

Move the bus clock Enable/Disable calls to be part
of the clock control logic so that they can be disabled
when they are not used.

Change-Id: I1a498db5ff132108134d356239fdc03721cac67b
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>