touchscreen: Fix build of da9034

Missing an include and thus breaks the x86-64 build.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/input/touchscreen/da9034-ts.c b/drivers/input/touchscreen/da9034-ts.c
index 4342e77..fa67d78 100644
--- a/drivers/input/touchscreen/da9034-ts.c
+++ b/drivers/input/touchscreen/da9034-ts.c
@@ -16,6 +16,7 @@
 #include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <linux/input.h>
+#include <linux/workqueue.h>
 #include <linux/mfd/da903x.h>
 
 #define DA9034_MANUAL_CTRL	0x50