net: ath9k: Use NULL instead of false

The function returns a pointer. Hence return NULL instead of false.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -392,7 +392,7 @@ static struct pri_sequence *pri_detector_add_pulse(struct pri_detector *de,
 
 	if (!pseq_handler_create_sequences(de, ts, max_updated_seq)) {
 		pri_detector_reset(de, ts);
-		return false;
+		return NULL;
 	}
 
 	ps = pseq_handler_check_detection(de);