ARM: dts: msm: add misc_ahb clock entries for msm8994

The misc_ahb clock is needed for DSI controller to
support "idle power collapse" feature on command mode
panels. Add this clock entry for both the
dsi controllers on 8994 platform.

Change-Id: Id4b6fedca7b8f0e591e5a0408f903e2d36de0928
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>