md: Add module.h to all files using it implicitly

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

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 37a3726..69c966f 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -6,6 +6,7 @@
  */
 
 #include <linux/slab.h>
+#include <linux/module.h>
 
 #include "md.h"
 #include "raid1.h"