ath79: fix wmac memory region for qca953x

According to /arch/mips/include/asm/mach-ath79/ar71xx_regs.h
the size of wmac register range for qca953x is only 0x20000.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>

target/linux/ath79/dts/qca953x.dtsi

@@ -173,7 +173,7 @@
 
 			wmac: wmac@18100000 {
 				compatible = "qca,qca9530-wmac";
-				reg = <0x18100000 0x230000>;
+				reg = <0x18100000 0x20000>;
 
 				interrupt-parent = <&intc2>;
 				interrupts = <0>;