clk: qcom: Add the clock controllers DT support for SDM660

Add DT files for global clock controller, multimedia clock
controller and peripheral gpu clock drivers to support gpu
PLLs and RCGs.
This snapshot of the gcc-sdm660, gpu-sdm660
and  mmcc-sdm660  DT as of msm-4.14 'commit
4d7da9f5ed3ac19c8 (" Merge "defconfig: sa8195: Enable
config for dyn splash"")'.

Change-Id: I7f32a5cfc037d7d91738d5b36aad2f97964bf2c4
Signed-off-by: Taniya Das <tdas@codeaurora.org>