dt-bindings: net: mdio-mux-gpio: Drop undocumented "marvell,reg-init"

"marvell,reg-init" is not yet documented by schema. It's irrelevant to
the example, so just drop it.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20241113225713.1784118-2-robh@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>