arm64: dts: renesas: beacon-renesom: Update Ethernet PHY ID

arm64: dts: renesas: beacon-renesom: Update Ethernet PHY ID

Due to the part shortage, the AR8031 PHY was replaced with a Micrel
KSZ9131.  Hard-coding the ID of the PHY makes this new PHY
non-operational on newer hardware.  Since previous hardware had only
shipped to a limited number of people, and they have not gone to
production, it should be safe to update the PHY ID.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230114225647.227972-2-aford173@gmail.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>