ARM: dts: msm: Remove usage of diff ref clk for sdxhedgehog

Remove input and control of the DIFF/CML reference clk to
qusb2 phy for sdxhedgehog, as we use SE/CMOS clk instead.

Change-Id: I4d014aa8608d5544b663dcf7522b6f92a12a570b
Signed-off-by: Devdutt Patnaik <dpatnaik@codeaurora.org>