serial-port: forcing to close a port is an internal operation

Ports being forced to get closed will only happen when we get a HUP error
in the serial port (e.g. device got disconnected).

src/mm-serial-port.c

@@ -35,6 +35,7 @@
 #include "mm-log.h"
 
 static gboolean mm_serial_port_queue_process (gpointer data);
+static void mm_serial_port_close_force (MMSerialPort *self);
 
 G_DEFINE_TYPE (MMSerialPort, mm_serial_port, MM_TYPE_PORT)
 
@@ -1055,7 +1056,7 @@ mm_serial_port_close (MMSerialPort *self)
     g_clear_object (&priv->cancellable);
 }
 
-void
+static void
 mm_serial_port_close_force (MMSerialPort *self)
 {
     MMSerialPortPrivate *priv;
@@ -1527,7 +1528,6 @@ dispose (GObject *object)
         priv->timeout_id = 0;
     }
 
-    if (mm_serial_port_is_open (MM_SERIAL_PORT (object)))
     mm_serial_port_close_force (MM_SERIAL_PORT (object));
 
     mm_serial_port_flash_cancel (MM_SERIAL_PORT (object));

src/mm-serial-port.h

@@ -117,8 +117,6 @@ gboolean mm_serial_port_open              (MMSerialPort *self,
 
 void     mm_serial_port_close             (MMSerialPort *self);
 
-void     mm_serial_port_close_force       (MMSerialPort *self);
-
 gboolean mm_serial_port_flash             (MMSerialPort *self,
                                            guint32 flash_time,
                                            gboolean ignore_errors,