ath9k: remove useless NULL initialisers

When I added .set_frag_threshold I didn't realise it was already
there which now generated a sparse warning. Therefore, remove
the .set_frag_threshold NULL initialiser, and while at it all the
other useless ones.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath9k/main.c

@@ -1648,20 +1648,12 @@ static struct ieee80211_ops ath9k_ops = {
 	.config 	    = ath9k_config,
 	.config_interface   = ath9k_config_interface,
 	.configure_filter   = ath9k_configure_filter,
-	.get_stats          = NULL,
 	.sta_notify         = ath9k_sta_notify,
 	.conf_tx 	    = ath9k_conf_tx,
-	.get_tx_stats 	    = NULL,
 	.bss_info_changed   = ath9k_bss_info_changed,
-	.set_tim            = NULL,
 	.set_key            = ath9k_set_key,
-	.hw_scan            = NULL,
-	.get_tkip_seq       = NULL,
-	.set_rts_threshold  = NULL,
-	.set_frag_threshold = NULL,
 	.get_tsf 	    = ath9k_get_tsf,
 	.reset_tsf 	    = ath9k_reset_tsf,
-	.tx_last_beacon     = NULL,
 	.ampdu_action       = ath9k_ampdu_action,
 	.set_frag_threshold = ath9k_no_fragmentation,
 };