ath9k_hw: fix antenna diversity on AR9285

On AR9285, the antenna switch configuration register uses more than just
16 bits. Because of an arbitrary mask applied to the EEPROM value that
stores this configuration, diversity was broken in some cases, leading
to a significant degradation in signal strength.
Fix this by changing the callback to return a 32 bit value and remove
the arbitrary mask.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/eeprom_def.c b/drivers/net/wireless/ath/ath9k/eeprom_def.c
index 77b1433..60480a1 100644
--- a/drivers/net/wireless/ath/ath9k/eeprom_def.c
+++ b/drivers/net/wireless/ath/ath9k/eeprom_def.c
@@ -1438,14 +1438,14 @@
 	return num_ant_config;
 }
 
-static u16 ath9k_hw_def_get_eeprom_antenna_cfg(struct ath_hw *ah,
+static u32 ath9k_hw_def_get_eeprom_antenna_cfg(struct ath_hw *ah,
 					       struct ath9k_channel *chan)
 {
 	struct ar5416_eeprom_def *eep = &ah->eeprom.def;
 	struct modal_eep_header *pModal =
 		&(eep->modalHeader[IS_CHAN_2GHZ(chan)]);
 
-	return pModal->antCtrlCommon & 0xFFFF;
+	return pModal->antCtrlCommon;
 }
 
 static u16 ath9k_hw_def_get_spur_channel(struct ath_hw *ah, u16 i, bool is2GHz)