ARM: dts: msm: Set USB UTMI clock rate on MSM8994

The USB3 controller should operate with a 19.2MHz mock UTMI
clock, not 60MHz. Remove the 'qcom,utmi-clk-rate' property
and let the default of 19.2MHz apply.

Change-Id: Ib23ccddc7f8638f81c2878387cfc86c9043d125a
Signed-off-by: Jack Pham <jackp@codeaurora.org>