clk: qcom: clock-gcc-8916: add display clock support for

 MSM8916

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: I29f0b59ca6acaa35b16b55e11fbb7686bc47164e
Signed-off-by: Taniya Das <tdas@codeaurora.org>