xen: Add module.h to modular drivers/xen users.

Previously these drivers just got module.h implicitly, but we
are cleaning that up and it will be no longer.  Call out the
real users of it.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/xen/balloon.c

@@ -39,6 +39,7 @@
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/errno.h>
+#include <linux/module.h>
 #include <linux/mm.h>
 #include <linux/bootmem.h>
 #include <linux/pagemap.h>

drivers/xen/xen-pciback/conf_space.c

@@ -10,6 +10,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/pci.h>
 #include "pciback.h"
 #include "conf_space.h"

drivers/xen/xenbus/xenbus_probe.c

@@ -46,6 +46,7 @@
 #include <linux/mutex.h>
 #include <linux/io.h>
 #include <linux/slab.h>
+#include <linux/module.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>

drivers/xen/xenbus/xenbus_probe_frontend.c

@@ -13,6 +13,7 @@
 #include <linux/kthread.h>
 #include <linux/mutex.h>
 #include <linux/io.h>
+#include <linux/module.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>