ARM: dts: da850-lcdk: Add ethernet0 alias to DT

In order to avoid Linux generating a random mac address on every boot,
add an ethernet0 alias that will allow u-boot to patch the dtb with
the MAC address programmed into the EEPROM.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>