ath9k: fix memory leak in DFS pattern detector

Free instance of pattern detector if requested DFS domain is
not supported.

Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -295,6 +295,7 @@ dfs_pattern_detector_init(enum nl80211_dfs_regions region)
 		return dpd;
 
 	pr_err("Could not set DFS domain to %d. ", region);
+	kfree(dpd);
 	return NULL;
 }
 EXPORT_SYMBOL(dfs_pattern_detector_init);