ath5k: beacon interval is in TU

the beacon interval is passed by mac80211 in TU already, so we can directly use
it without conversion. also update the comments about TU (1 TU is defined by
802.11 as 1024usec).

drivers/net/wireless/ath5k/ath5k.h:     Changes-licensed-under: ISC
drivers/net/wireless/ath5k/base.c:      Changes-licensed-under: 3-Clause-BSD
drivers/net/wireless/ath5k/base.h:      Changes-licensed-under: 3-Clause-BSD

Signed-off-by: Bruno Randolf <bruno@thinktube.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath5k/base.h b/drivers/net/wireless/ath5k/base.h
index 7ba2223..20c9469 100644
--- a/drivers/net/wireless/ath5k/base.h
+++ b/drivers/net/wireless/ath5k/base.h
@@ -164,7 +164,7 @@
 	struct ath5k_buf	*bbuf;		/* beacon buffer */
 	unsigned int		bhalq,		/* SW q for outgoing beacons */
 				bmisscount,	/* missed beacon transmits */
-				bintval,	/* beacon interval */
+				bintval,	/* beacon interval in TU */
 				bsent;
 
 	struct timer_list	calib_tim;	/* calibration timer */