Fix a return code check for ath9k_hw_nvram_read, this function returns
AH_TRUE when the call succeeded

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

--- a/drivers/net/wireless/ath9k/hw.c
+++ b/drivers/net/wireless/ath9k/hw.c
@@ -803,7 +803,7 @@
 		u_int16_t magic, magic2;
 		int addr;
 
-		if (ath9k_hw_nvram_read(ah, AR5416_EEPROM_MAGIC_OFFSET,
+		if (!ath9k_hw_nvram_read(ah, AR5416_EEPROM_MAGIC_OFFSET,
 					&magic)) {
 			HDPRINTF(ah, HAL_DBG_EEPROM,
 				 "%s: Reading Magic # failed\n", __func__);