avr32: atngw100: remove useless include

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>

arch/avr32/boards/atngw100/mrmt.c

@@ -21,7 +21,6 @@
 #include <linux/leds_pwm.h>
 #include <linux/input.h>
 #include <linux/gpio_keys.h>
-#include <linux/atmel_serial.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/ads7846.h>