arm64: dts: ti: k3-j784s4: Add overlay for dual port USXGMII mode

arm64: dts: ti: k3-j784s4: Add overlay for dual port USXGMII mode

The CPSW9G instance of the CPSW Ethernet Switch supports USXGMII mode
with MAC Ports 1 and 2 of the instance, which are connected to ENET
Expansion 1 and ENET Expansion 2 slots on the EVM respectively, through
the Serdes2 instance of the SERDES.

Enable CPSW9G MAC Ports 1 and 2 in fixed-link configuration USXGMII mode
at 5 Gbps each.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Chintan Vankar <c-vankar@ti.com>
Link: https://lore.kernel.org/r/20240502091002.3659435-6-c-vankar@ti.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>