mac80211: remove hw.conf.channel usage where possible

Removes hw.conf.channel usage from the following functions:
 * ieee80211_mandatory_rates
 * ieee80211_sta_get_rates
 * ieee80211_frame_duration
 * ieee80211_rts_duration
 * ieee80211_ctstoself_duration

This is in preparation for multi-channel operation.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/b43legacy/xmit.c b/drivers/net/wireless/b43legacy/xmit.c
index e6c573a..a8012f2 100644
--- a/drivers/net/wireless/b43legacy/xmit.c
+++ b/drivers/net/wireless/b43legacy/xmit.c
@@ -228,6 +228,7 @@
 	} else {
 		txhdr->dur_fb = ieee80211_generic_frame_duration(dev->wl->hw,
 							 info->control.vif,
+							 info->band,
 							 fragment_len,
 							 rate_fb);
 	}