ath9k_hw: Fix memory leak on ath9k_hw_rf_alloc_ext_banks failure

The allocated externel radio banks have to be freed in
case of ath9k_hw_rf_alloc_ext_banks failure.

Cc: stable@kernel.org
Signed-off-by: Rajkumar Manoharan <rmanoharan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -484,6 +484,7 @@ static int ath9k_hw_post_init(struct ath_hw *ah)
 		ath_print(ath9k_hw_common(ah), ATH_DBG_FATAL,
 			  "Failed allocating banks for "
 			  "external radio\n");
+		ath9k_hw_rf_free_ext_banks(ah);
 		return ecode;
 	}