ARM: dts: imx6dl-icore-rqs: Fix invalid PHY address assignment for ethernet

Add "reg" property for ethernet to fix this issue.

Errors in boot logs:
mdio_bus 2188000.ethernet-1:
/soc/aips-bus@02100000/ethernet@02188000/mdio/ethernet-phy
has invalid PHY address

mdio_bus 2188000.ethernet-1: scan phy ethernet-phy at address 0
mdio_bus 2188000.ethernet-1: scan phy ethernet-phy at address 1
mdio_bus 2188000.ethernet-1: scan phy ethernet-phy at address 2
mdio_bus 2188000.ethernet-1: scan phy ethernet-phy at address 3

Reported-by: Shyam Saini <shyam@amarulasolutions.com>
Suggested-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Shyam Saini <shyam@amarulasolutions.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>