mfd: Add module.h to the implicit drivers/mfd users

With the pending module.h cleanup, these files will fail to compile,
unless they explicitly call out the include of this file.

[omap-usb-host addition courtesy of Anand Gadiyar <gadiyar@ti.com>]

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/mfd/max8997.c b/drivers/mfd/max8997.c
index f83103b..50ad93b 100644
--- a/drivers/mfd/max8997.c
+++ b/drivers/mfd/max8997.c
@@ -24,6 +24,7 @@
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/pm_runtime.h>
+#include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/mfd/core.h>
 #include <linux/mfd/max8997.h>