mac80211: Remove unnused throughput field from minstrel_rate.

I noticed that the throughput field of the minstrel_rate struct is never used,
so remove it.
Signed-off-by: Arnd Hannemann <hannemann@nets.rwth-aachen.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/rc80211_minstrel.h

@@ -33,7 +33,6 @@ struct minstrel_rate {
 
 	/* per-rate throughput */
 	u32 cur_tp;
-	u32 throughput;
 
 	u64 succ_hist;
 	u64 att_hist;