arm64: renesas: Disable AVB1 and AVB2 on R8A779G0 V4H White Hawk board

arm64: renesas: Disable AVB1 and AVB2 on R8A779G0 V4H White Hawk board

The U-Boot is currently not capable of handling ethernet-phy-ieee802.3-c45
PHYs correctly, and also does not handle MDIO bus wide reset-gpios property.
Until proper C45 PHY support lands in U-Boot, disable AVB1/AVB2 interfaces.
This only disables the two MACs with 88Q2110/88Q2112 100/1000BASE-T1 PHYs
on ethenet sub-board, the main board AVB0 ethernet is unaffected.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>