hostapd: Global control interface notifications

This commit implements hostapd global control interface notifications
infrastructure. hostapd global control interface clients issue
ATTACH/DETACH commands to register and deregister with hostapd
correspondingly - the same way as for any other hostapd/wpa_supplicant
control interface.

Bug: 24270573

Change-Id: I46da39e8262a446e7779a1adfbcb08b5bfa382d7
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
diff --git a/hostapd/main.c b/hostapd/main.c
index e36c948..62d0775 100644
--- a/hostapd/main.c
+++ b/hostapd/main.c
@@ -561,6 +561,7 @@
 	interfaces.global_iface_path = NULL;
 	interfaces.global_iface_name = NULL;
 	interfaces.global_ctrl_sock = -1;
+	interfaces.global_ctrl_dst = NULL;
 
 	for (;;) {
 		c = getopt(argc, argv, "b:Bde:f:hKP:Ttu:vg:G:");