ASoC: sam9g20_wm8731: remove useless mach/gpio.h

This include file is about to disapear. In addition it is
useless for this code. So it is time to remove it.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Mark Brown <broonie@linaro.org>

sound/soc/atmel/sam9g20_wm8731.c

@@ -48,7 +48,6 @@
 
 #include <asm/mach-types.h>
 #include <mach/hardware.h>
-#include <mach/gpio.h>
 
 #include "../codecs/wm8731.h"
 #include "atmel-pcm.h"