dt-bindings: net: realtek,rtl82xx: Document RTL8211F LED support

The RTL8211F PHY does support LED configuration, document support
for LEDs in the binding document.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20240708211649.165793-1-marex@denx.de


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