dt-bindings: net: phy: Document LED inactive high impedance mode

Document LED inactive high impedance mode to set the LED to require high
impedance configuration to be turned OFF.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Lee Jones <lee@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240125203702.4552-3-ansuelsmth@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/leds/common.yaml

@@ -206,6 +206,12 @@ properties:
       Makes LED active low. To turn the LED ON, line needs to be
       set to low voltage instead of high.
 
+  inactive-high-impedance:
+    type: boolean
+    description:
+      Set LED to high-impedance mode to turn the LED OFF. LED might also
+      describe this mode as tristate.
+
   # Required properties for flash LED child nodes:
   flash-max-microamp:
     description: