arm64: dts: ti: k3-j7200-mcu: add mcu cpsw nuss node

Add DT node for The TI J7200 MCU SoC Gigabit Ethernet two ports Switch
subsystem (MCU CPSW NUSS).

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Suman Anna <s-anna@ti.com>
Link: https://lore.kernel.org/r/20200923220938.30788-4-grygorii.strashko@ti.com