ARM: dts: msm: Add usb pipe clock source clk on kona

USB SS phy driver needs to toggle between bi_tcxo
and phy pipe clock as part of its CX collapse sequence,
add pipe_clk_src which would be set to parent as
ref_clk_src or pipe_clk.

Change-Id: I78624b559df51063761773606e6e636a65e740e4