dt-bindings: net: Add support for rk3576 dwmac

Add a rockchip,rk3576-gmac compatible for supporting the 2 gmac
devices on the rk3576.

Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20240823141318.51201-3-detlev.casanova@collabora.com


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