clk: qcom: clock-gcc-ferrum: Add display clock support for msmferrum

Model the DSI clocks in GCC as a separate device. The byte and pixel clocks
exposed by the DSI PLL device is needed by the GCC DSI clocks. Finally, the
DSI controller can get the clocks exposed by GCC DSI. So, the order of
probes for this to work is GCC->DSI  PLL->GCC_MDSS_DSI->DSI controller.

Change-Id: Id998201cc352d6785dfe54efd5f40397be09322d
Signed-off-by: Janani Venkataraman <jananiv@codeaurora.org>