drivers/gpio: Fix drivers who are implicit users of module.h

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

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/gpio/gpio-ml-ioh.c b/drivers/gpio/gpio-ml-ioh.c
index 3aa6bee..ea8e738 100644
--- a/drivers/gpio/gpio-ml-ioh.c
+++ b/drivers/gpio/gpio-ml-ioh.c
@@ -14,6 +14,7 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
  */
+#include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/pci.h>