ARM: dts: Fix dm814x missing phy-cells property

We have phy-cells for usb_phy0, but it's missing for usb_phy1 and we get:

Warning (phys_property): Missing property '#phy-cells' in node
/ocp/l4ls@48000000/control@140000/usb-phy@1b00 or bad phandle
(referred from /ocp/usb@47400000/usb@47401800:phys[0])

Signed-off-by: Tony Lindgren <tony@atomide.com>