Merged in plwm/nuttx/stm32f746g-disco-touchscreen (pull request #701)

stm32f746g-disco: touchscreen support

* fixed FT5x06 driver to correctly close (previously it unregistered interrupt handler during close)
* added LittlevGL demo for STM32F746G-DISCO

Approved-by: GregoryN <gnutt@nuttx.org>

drivers/input/ft5x06.c

@@ -780,10 +780,6 @@ static void ft5x06_shutdown(FAR struct ft5x06_dev_s *priv)
 
   config->clear(config);
   config->enable(config, false);
-
-  /* Attach the interrupt handler */
-
-  (void)config->attach(config, NULL, NULL);
 #endif
 }