drivers/isdn: Add module.h to ISDN files implicitly using it.

So that we don't get build failures once the implicit module.h
presence is terminated.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/isdn/hardware/mISDN/mISDNisar.c b/drivers/isdn/hardware/mISDN/mISDNisar.c
index d13fa5b..7034af2 100644
--- a/drivers/isdn/hardware/mISDN/mISDNisar.c
+++ b/drivers/isdn/hardware/mISDN/mISDNisar.c
@@ -29,6 +29,7 @@
 #include <linux/delay.h>
 #include <linux/vmalloc.h>
 #include <linux/mISDNhw.h>
+#include <linux/module.h>
 #include "isar.h"
 
 #define ISAR_REV	"2.1"