ARM: dts: msm: Add proper ref_clk for qusb phy for SM6150

This change adds designated reference clocks for both
primary and secondary qusb phys.

Change-Id: Iff9147e17a3f6703f1118e6f2d032d266cab1035
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>