ath79: wr2543: add compatible string for wifi

Makes it clear that the calibration size is correct as most ar72xx
devices use older wifi chips.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/17278
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/ath79/dts/ar7242_tplink_tl-wr2543-v1.dts

@@ -159,6 +159,7 @@
 	status = "okay";
 
 	ath9k: wifi@0,0 {
+		compatible = "pci168c,0030";
 		reg = <0x0000 0 0 0 0>;
 		#gpio-cells = <2>;
 		gpio-controller;