media: dt-bindings: adv748x: Fix decimal unit addresses

With recent dtc and W=1:

    Warning (graph_port): video-receiver@70/port@10: graph node unit address error, expected "a"
    Warning (graph_port): video-receiver@70/port@11: graph node unit address error, expected "b"

Unit addresses are always hexadecimal (without prefix), while the bases
of reg property values depend on their prefixes.

Fixes: e6959517 ("media: adv748x: Add adv7481, adv7482 bindings")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/devicetree/bindings/media/i2c/adv748x.txt

@@ -73,7 +73,7 @@ Example:
 			};
 		};
 
-		port@10 {
+		port@a {
 			reg = <10>;
 
 			adv7482_txa: endpoint {
@@ -83,7 +83,7 @@ Example:
 			};
 		};
 
-		port@11 {
+		port@b {
 			reg = <11>;
 
 			adv7482_txb: endpoint {