fix(NCM): set default NCM mode is connect, add notify judgement

1. Set default network state is connected, in case not actively call tud_network_connect
2. The application layer can get the call result

src/class/net/ncm_device.c

@@ -158,7 +158,8 @@ tu_static ncm_interface_t ncm_interface;
 
 static void ncm_report(void);
 
-uint8_t network_state;
+// default network state is connected, in case not actively call tud_network_connect
+static uint8_t network_state = NETWORK_CONNECTED;
 
 /*
  * Set up the NTB state in ncm_interface to be ready to add datagrams.
@@ -250,18 +251,40 @@ void tud_network_recv_renew(void)
   tud_network_recv_cb(receive_ntb + ndp->datagram[i].wDatagramIndex, ndp->datagram[i].wDatagramLength);
 }
 
-void tud_network_disconnect(void)
+bool tud_network_disconnect(void)
 {
-    network_state = NETWORK_DISCONNECT;
+  // already disconnected
+  if (network_state == NETWORK_DISCONNECT) {
+    return true;
+  }
+
+  if (!ncm_interface.report_pending) {
     ncm_interface.report_state = REPORT_CONNECTED;
+    network_state = NETWORK_DISCONNECT;
     ncm_report();
+  } else {
+    // busy...
+    return false;
+  }
+  return true;
 }
 
-void tud_network_connect(void)
+bool tud_network_connect(void)
 {
-    network_state = NETWORK_CONNECTED;
+  // already connected
+  if (network_state == NETWORK_CONNECTED) {
+    return true;
+  }
+
+  if (!ncm_interface.report_pending) {
     ncm_interface.report_state = REPORT_CONNECTED;
+    network_state = NETWORK_CONNECTED;
     ncm_report();
+    return true;
+  } else {
+    // busy...
+    return false;
+  }
 }
 
 //--------------------------------------------------------------------+

src/class/net/net_device.h

@@ -77,12 +77,6 @@ bool tud_network_can_xmit(uint16_t size);
 // if network_can_xmit() returns true, network_xmit() can be called once
 void tud_network_xmit(void *ref, uint16_t arg);
 
-// indicate to network disconnect
-void tud_network_disconnect(void);
-
-// indicate to network connect
-void tud_network_connect(void);
-
 //--------------------------------------------------------------------+
 // Application Callbacks (WEAK is optional)
 //--------------------------------------------------------------------+
@@ -107,6 +101,12 @@ extern uint8_t tud_network_mac_address[6];
 // callback to client providing optional indication of internal state of network driver
 void tud_network_link_state_cb(bool state);
 
+// indicate to network disconnect, only work in NCM
+bool tud_network_disconnect(void);
+
+// indicate to network connect, only work in NCM
+bool tud_network_connect(void);
+
 //--------------------------------------------------------------------+
 // INTERNAL USBD-CLASS DRIVER API
 //--------------------------------------------------------------------+