Input: ads7846 - introduce platform specific way to synchronize sampling

Noises can be introduced when LCD signals are being driven, some platforms
provide a signal to assist the synchronization of this sampling procedure.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index 05eab2f..2ea2032 100644
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -51,5 +51,6 @@
 				 void **filter_data);
 	int	(*filter)	(void *filter_data, int data_idx, int *val);
 	void	(*filter_cleanup)(void *filter_data);
+	void	(*wait_for_sync)(void);
 };