arm64: dts: armada-3720-espressobin: Configure RGMII and SMI pins

In order to be able to communicate with the 88e6341 switch some pins
have to be repurposed as RGMII and SMI pins.

This fixes ethernet support on system booted via a bootloader that
has not already configured those pins (e.g. mainline u-boot, or vendor
u-boot compiled without ethernet support).

Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>