arm64: dts: ti: k3-j7200-main.dtsi: Add USB to SERDES lane MUX

The USB controller can be connected to one of the 2 lanes
of SERDES0 using a MUX. Add a MUX controller node for that.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200930122032.23481-4-rogerq@ti.com