FIX: move cdc polling out of main to the dedicated device-level polli…

…ng function

main.c

@@ -21,6 +21,5 @@ int main() {
     usb_init();
     while (1) {
         usb_poll();
-        usb_cdc_poll();
     }
 }

usb_core.c

@@ -54,6 +54,10 @@ void usb_device_handle_frame() {
     usb_cdc_frame();
 }
 
+void usb_device_poll() {
+    usb_cdc_poll();
+}
+
 /* Device Descriptor Requests Handling */
 
 usb_status_t usb_control_endpoint_process_get_descriptor(usb_setup_t *setup,

usb_core.h

@@ -47,5 +47,6 @@ void usb_device_handle_configured();
 void usb_device_handle_suspend();
 void usb_device_handle_wakeup();
 void usb_device_handle_frame();
+void usb_device_poll();
 
 #endif /* USB_CORE_H */

usb_io.c

@@ -260,4 +260,5 @@ void usb_poll() {
         }
         usb_device_handle_frame();
     }
+    usb_device_poll();
 }