regulator: Add module.h to drivers/regulator users as required

Another group of drivers that are taking advantage of the implicit
presence of module.h -- and will break when we pull the carpet out
from under them during a cleanup.  Fix 'em now.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/regulator/wm8400-regulator.c b/drivers/regulator/wm8400-regulator.c
index 0f12c70..71632dd 100644
--- a/drivers/regulator/wm8400-regulator.c
+++ b/drivers/regulator/wm8400-regulator.c
@@ -15,6 +15,7 @@
 #include <linux/bug.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/regulator/driver.h>
 #include <linux/mfd/wm8400-private.h>