dt-bindings: net: phy: vsc8531: Convert to DT schema

dt-bindings: net: phy: vsc8531: Convert to DT schema

Convert VSC8531 Gigabit ethernet phy binding to DT schema format. While
at it add compatible string for VSC8541 PHY which is very much similar
to the VSC8531 PHY and is already supported in the kernel. VSC8541 PHY
is present on the Renesas RZ/T2H EVK.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20251025064850.393797-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>