binder: Callback registration for interfaces

Add callback registration for each binder interface type:
ISupplicant, IIface, INetwork.

BUG: 30093041
Change-Id: I9043d9a033bcfbee5a80f61cf58e564249edf3a7
diff --git a/wpa_supplicant/binder/iface.h b/wpa_supplicant/binder/iface.h
index 13dd4b0..6db4609 100644
--- a/wpa_supplicant/binder/iface.h
+++ b/wpa_supplicant/binder/iface.h
@@ -46,6 +46,9 @@
 	    int network_id,
 	    android::sp<fi::w1::wpa_supplicant::INetwork> *network_object_out)
 	    override;
+	android::binder::Status RegisterCallback(
+	    const android::sp<fi::w1::wpa_supplicant::IIfaceCallback> &callback)
+	    override;
 
 private:
 	struct wpa_supplicant *retrieveIfacePtr();