band-steering: add band-steering component

This adds a new band-steering component to usteer.

With band-steering enabled, usteer will attempt to move clients with a
consistently good SNR / signal from 2.4 GHz to the 5 GHz band.

In contrast to existing policies usteer tracks, band-steering is
non-invasive and will not lead to forceful connection termination.

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

local_node.c

@@ -642,6 +642,7 @@ usteer_local_node_update(struct uloop_timeout *timeout)
 	usteer_local_node_state_reset(ln);
 	uloop_timeout_set(&ln->req_timer, 1);
 	usteer_local_node_kick(ln);
+	usteer_band_steering_perform_steer(ln);
 	uloop_timeout_set(timeout, config.local_sta_update);
 }