policy: make roam-steers client-rejectable

While usteer tries it's best to determine the availability of a better
node for a certain client, it might still attempt to direct the client
to a unsuitable AP.

Transition away from using BSS-Transition-Requests with the
disassoc-imminent bit set and instead unset this bit.

This way, the client can inform the AP it will not transition to a
different BSS but instead wishes to remain connected to the current AP.

usteer will still kick clients in case they either accepted the
BSS-transition-request and do not roam or ignore the request completely.

Signed-off-by: David Bauer <mail@david-bauer.net>

usteer.h

@@ -219,9 +219,6 @@ enum roam_trigger_state {
 	ROAM_TRIGGER_IDLE,
 	ROAM_TRIGGER_SCAN,
 	ROAM_TRIGGER_SCAN_DONE,
-	ROAM_TRIGGER_WAIT_KICK,
-	ROAM_TRIGGER_NOTIFY_KICK,
-	ROAM_TRIGGER_KICK,
 };
 
 struct sta_info {
@@ -254,6 +251,8 @@ struct sta_info {
 		uint64_t timestamp;
 	} bss_transition_response;
 
+	uint64_t kick_time;
+
 	int kick_count;
 
 	uint32_t below_min_snr;