ARM: dts: msm: Add src clk name in csiphy node

Currently csiphy driver finds the src clk index by parsing
through all the clock names. With this change we can find
the src clk index while parsing the DT, the driver no longer
needs to find it.

Change-Id: I49d6d70d8956c3c96e5e3349d0323c65f1345f6d
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>