ARM: dts: msm: Add support for DSI PLL 1 clocks for 8994

DSI PLL 1 needs to be turned off for certain targets. Adding support
to map and configure DSI PLL 1 registers and the clocks. At this point,
we don't plan on using the byte/pixel clocks but this can be extended
in the future.

Change-Id: I02a8350235446130070e6093beeb864cd9654513
Signed-off-by: Siddhartha Agrawal <agrawals@codeaurora.org>