ARM: dts: k3-am64-main: Add CPSW DT nodes

AM64 as CPSW3G IP with 2 external ports. Add DT entries for the same
(based on kernel DT).

Disable second port as its by default set to ICSS usage on EVM.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>