sta: add sta_connection_state enum

Make the connection state of a sta-info more readable by introducing an
enum for the STA connection state.

Also switch come comparison cases to use the explicit enum values to
make the code more readable.

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

usteer.h

@@ -54,6 +54,12 @@ enum usteer_node_type {
 	NODE_TYPE_REMOTE,
 };
 
+enum usteer_sta_connection_state {
+	STA_NOT_CONNECTED = 0,
+	STA_CONNECTED = 1,
+	STA_DISCONNECTED = 2,
+};
+
 struct sta_info;
 struct usteer_local_node;
 struct usteer_remote_host;