arm64: dts: renesas: rcar-gen3: Add missing Ethernet PHY resets

Describe all Ethernet PHY reset GPIOs on R-Car Gen3 boards, to avoid
relying solely on boot loaders to bring PHYs out of reset.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/3e6fd765850e8ef0980d8e98bc5f2126538d626f.1631177442.git.geert+renesas@glider.be