drivers/input: Add module.h to modular drivers implicitly using it

A pending cleanup will mean that module.h won't be implicitly
everywhere anymore.  Make sure the modular drivers in input dir
are actually calling out for <module.h> explicitly in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/input/touchscreen/ad7879-spi.c b/drivers/input/touchscreen/ad7879-spi.c
index ddf732f..b1643c8 100644
--- a/drivers/input/touchscreen/ad7879-spi.c
+++ b/drivers/input/touchscreen/ad7879-spi.c
@@ -9,6 +9,7 @@
 #include <linux/input.h>	/* BUS_SPI */
 #include <linux/pm.h>
 #include <linux/spi/spi.h>
+#include <linux/module.h>
 
 #include "ad7879.h"