dt-bindings: clock: adi,axi-clkgen: add clock-output-names property

Add an optional `clock-output-names` property to the ADI AXI Clock
Generator binding. This is already being used in the Linux driver and
real-world dtbs, so we should document it to allow for correct binding
validation.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20250811-dt-bindings-clk-axi-clkgen-add-clock-output-names-property-v1-1-f02727736aa7@baylibre.com
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/adi,axi-clkgen.yaml

@@ -42,6 +42,9 @@ properties:
           - const: clkin2
           - const: s_axi_aclk
 
+  clock-output-names:
+    maxItems: 1
+
   '#clock-cells':
     const: 0
 
@@ -65,4 +68,5 @@ examples:
       reg = <0xff000000 0x1000>;
       clocks = <&osc 1>, <&clkc 15>;
       clock-names = "clkin1", "s_axi_aclk";
+      clock-output-names = "spi_sclk";
     };