ARM: dts: keystone-k2g: Move usb-phy nodes out of soc0

The two usb-phy nodes are not memory-mapped devices on the
SoC but rather dummy phys for SoCs with transparent autonomous
NOP phys. Move these to outside soc0 to their own node like
done elsewhere.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>