Device nodes representing I/O devices should be marked disabled in the
SoC-specific DTS, and overridden by board-specific DTSes where needed.

Fixes: a92843c8 ("arm64: dts: r8a7795: add EthernetAVB device node")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>