ath9k: fix build error with disabled debug

DFS pulse interval printing is only available
when CONFIG_ATH9K_DEBUGFS is set.
Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -178,12 +178,14 @@ void ath9k_dfs_process_phyerr(struct ath_softc *sc, void *data,
 	pe.ts = mactime;
 	if (ath9k_postprocess_radar_event(sc, &ard, &pe)) {
 		struct dfs_pattern_detector *pd = sc->dfs_detector;
+#ifdef CONFIG_ATH9K_DEBUGFS
 		ath_dbg(common, DFS,
 			"ath9k_dfs_process_phyerr: channel=%d, ts=%llu, "
 			"width=%d, rssi=%d, delta_ts=%llu\n",
 			pe.freq, pe.ts, pe.width, pe.rssi,
 			pe.ts - sc->debug.stats.dfs_stats.last_ts);
 		sc->debug.stats.dfs_stats.last_ts = pe.ts;
+#endif
 		DFS_STAT_INC(sc, pulses_processed);
 		if (pd != NULL && pd->add_pulse(pd, &pe)) {
 			DFS_STAT_INC(sc, radar_detected);