ARM: dts: rk3228-evb: Enable the integrated PHY for gmac

This patch enables the integrated PHY for rk3228 evb board
by default.
To use the external 1000M PHY on evb board, need to make
some switch of evb board to be on.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>