wifi: mac80211: Remove unused function declarations

Commit 68542962 ("mac80211: Fix circular locking dependency in
ARP filter handling") left the ieee80211_set_arp_filter() declaration
unused.
And commit 164eb02d ("mac80211: add radar detection command/event")
introducted ieee80211_dfs_cac_timer() declaration but never implemented
it.
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230801134337.24452-1-yuehaibing@huawei.com
[reword commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -1872,7 +1872,6 @@ void ieee80211_send_pspoll(struct ieee80211_local *local,
 			   struct ieee80211_sub_if_data *sdata);
 void ieee80211_recalc_ps(struct ieee80211_local *local);
 void ieee80211_recalc_ps_vif(struct ieee80211_sub_if_data *sdata);
-int ieee80211_set_arp_filter(struct ieee80211_sub_if_data *sdata);
 void ieee80211_sta_work(struct ieee80211_sub_if_data *sdata);
 void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
 				  struct sk_buff *skb);
@@ -2564,7 +2563,6 @@ void ieee80211_recalc_chanctx_min_def(struct ieee80211_local *local,
 				      struct ieee80211_link_data *rsvd_for);
 bool ieee80211_is_radar_required(struct ieee80211_local *local);
 
-void ieee80211_dfs_cac_timer(unsigned long data);
 void ieee80211_dfs_cac_timer_work(struct work_struct *work);
 void ieee80211_dfs_cac_cancel(struct ieee80211_local *local);
 void ieee80211_dfs_radar_detected_work(struct work_struct *work);