ramips: add missing DTS frequency limit for the 5 GHz radio on Archer C20i

Signed-off-by: Felix Fietkau <[email protected]>

target/linux/ramips/dts/ArcherC20i.dts

@@ -153,5 +153,6 @@
 	mt76@0,0 {
 		reg = <0x0000 0 0 0 0>;
 		mediatek,mtd-eeprom = <&radio 32768>;
+		ieee80211-freq-limit = <5000000 6000000>;
 	};
 };