measurement: add handling of measurements

Add logic for saving measurement-reports from STAs.

This commit does not yet save the measurement-reports received from
clients but adds the necessary code to do so. Currently the codes can
only handle beacon-reports, but link measurements can be added to it in
the future.

It also adds the new config-key measurement_report_timeout which
controls how long measurements are saved upon they are received by a
STA.

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

main.c

@@ -86,6 +86,7 @@ void usteer_init_defaults(void)
 
 	config.sta_block_timeout = 30 * 1000;
 	config.local_sta_timeout = 120 * 1000;
+	config.measurement_report_timeout = 120 * 1000;
 	config.local_sta_update = 1 * 1000;
 	config.max_retry_band = 5;
 	config.max_neighbor_reports = 8;