net/: Fix some incorrect comments that go back for years (but have also been cloned in newer files). The network was once interrupt driver, but now runs on the work queue with a semaphore to enforce mutual exclusion.

net/usrsock/usrsock_conn.c

@@ -121,9 +121,7 @@ FAR struct usrsock_conn_s *usrsock_alloc(void)
 {
   FAR struct usrsock_conn_s *conn;
 
-  /* The free list is only accessed from user, non-interrupt level and
-   * is protected by a semaphore (that behaves like a mutex).
-   */
+  /* The free list is protected by a semaphore (that behaves like a mutex). */
 
   _usrsock_semtake(&g_free_sem);
   conn = (FAR struct usrsock_conn_s *)dq_remfirst(&g_free_usrsock_connections);
@@ -158,9 +156,7 @@ FAR struct usrsock_conn_s *usrsock_alloc(void)
 
 void usrsock_free(FAR struct usrsock_conn_s *conn)
 {
-  /* The free list is only accessed from user, non-interrupt level and
-   * is protected by a semaphore (that behaves like a mutex).
-   */
+  /* The free list is protected by a semaphore (that behaves like a mutex). */
 
   DEBUGASSERT(conn->crefs == 0);