ARM: dts: rk3228-evb: Fix the compiling error

This patch solves the following error:
arch/arm/boot/dts/rk3228-evb.dtb: ERROR (phandle_references): Reference to non-existent node or label "phy0"

Fixess db40f15b

 ("ARM: dts: rk3228-evb: Enable the integrated PHY for gmac")
Signed-off-by: David Wu <david.wu@rock-chips.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>