dt-bindings: leds: Document "netdev" trigger

Document the "netdev" trigger which is used to control LEDs by
network device activity. This is an existing trigger used in
existing DTs, document it so validation of those DTs would pass.
Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240708114653.18566-1-marex@denx.deSigned-off-by: Lee Jones <lee@kernel.org>

Documentation/devicetree/bindings/leds/common.yaml

@@ -113,6 +113,8 @@ properties:
             # LED indicates NAND memory activity (deprecated),
             # in new implementations use "mtd"
           - nand-disk
+            # LED indicates network activity
+          - netdev
             # No trigger assigned to the LED. This is the default mode
             # if trigger is absent
           - none