ARM: dts: msm: Add usb3-host phandle to apq8084_dock device

Add a phandle to the secondary USB controller to the apq8084_dock
device. This is to allow for the USB device to be dynamically
removed/added on demand when the dock connected.

Change-Id: I29bce625afc159311d3cf85d1941ad182d761bcb
Signed-off-by: Jack Pham <jackp@codeaurora.org>