ramips: fix EW-7478AC model name in DTS

This fixes lower case AC in the DTS model name.

Fixes: 88f7a29f ("ramips: add support for Edimax EW-7476RPC / EW-7478AC")
Reported-by: Cezary Jackiewicz <cezary@eko.one.pl>
Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/ramips/dts/EW-7478AC.dts

@@ -6,7 +6,7 @@
 
 / {
 	compatible = "edimax,ew-7478ac", "ralink,mt7620a-soc";
-	model = "Edimax EW-7478ac";
+	model = "Edimax EW-7478AC";
 
 	leds {
 		compatible = "gpio-leds";