ath9k_hw: add default chainmask for AR9462

the default tx/rx chainmask for AR9462 is 0x3.
this patch helps to assign 0x3 rather than 0x7 for
AR9462 with the help of fix_chainmask module if something
goes wrong in reading tx/rx chain mask from OTP/EEPROM
card(though its very unlikely)
Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/hw.c

@@ -2312,6 +2312,8 @@ int ath9k_hw_fill_cap_info(struct ath_hw *ah)
 
 	if (AR_SREV_9485(ah) || AR_SREV_9285(ah) || AR_SREV_9330(ah))
 		chip_chainmask = 1;
+	else if (AR_SREV_9462(ah))
+		chip_chainmask = 3;
 	else if (!AR_SREV_9280_20_OR_LATER(ah))
 		chip_chainmask = 7;
 	else if (!AR_SREV_9300_20_OR_LATER(ah) || AR_SREV_9340(ah))