arm64: dts: ti: k3-am642-sk: Add CPSW DT nodes

AM642 SK board has 2 CPSW3g ports connected through TI DP83867 PHYs. Add DT
entries for the same.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210304211038.12511-5-grygorii.strashko@ti.com