ath9k: simplify DFS pulse interval debug printing

Make DFS pulse interval calculation independent
from CONFIG_ATH9K_DEBUGFS.

Signed-off-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index b204694..2ca8f7e 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -770,6 +770,7 @@
 	struct ath_ant_comb ant_comb;
 	u8 ant_tx, ant_rx;
 	struct dfs_pattern_detector *dfs_detector;
+	u64 dfs_prev_pulse_ts;
 	u32 wow_enabled;
 	/* relay(fs) channel for spectral scan */
 	struct rchan *rfs_chan_spec_scan;