wimax/i2400m: when stopping the device, cancel any pending message

The stop procedure for the device must make sure that any task that is
waiting on a message is properly cancelled.

This was being taken care of only by the __i2400m_dev_reset_handle()
path and the rest was working by chance because the waits have a
timeout.

Fixed by adding a proper cancellation in __i2400m_dev_stop().
Signed-off-by: Inaky Perez-Gonzalez <inaky@linux.intel.com>

drivers/net/wimax/i2400m/driver.c

@@ -537,6 +537,8 @@ void __i2400m_dev_stop(struct i2400m *i2400m)
 
 	d_fnstart(3, dev, "(i2400m %p)\n", i2400m);
 	wimax_state_change(wimax_dev, __WIMAX_ST_QUIESCING);
+	i2400m_msg_to_dev_cancel_wait(i2400m, -EL3RST);
+	complete(&i2400m->msg_completion);
 	i2400m_net_wake_stop(i2400m);
 	i2400m_dev_shutdown(i2400m);
 	/*