arm64: dts: renesas: falcon: Move AVB0 to main DTS

The Ethernet PHY for the first AVB instance is located on the Falcon
BreakOut board.  Hence move its description from the DTS file that
describes the CPU board to the main Falcon DTS file.

Fixes: e8ac55a5 ("arm64: dts: renesas: falcon: Add Ethernet-AVB0 support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20210316154705.2433528-4-geert+renesas@glider.be