lguest: add export.h to lguest files for THIS_MODULE/EXPORT_SYMBOL

We need this in advance of the module.h cleanup, or we'll
get compile errors like this:

  CC      drivers/lguest/lguest_device.o
drivers/lguest/lguest_device.c: In function ‘lguest_devices_init’:
drivers/lguest/lguest_device.c:490: error: ‘THIS_MODULE’ undeclared (first use in this function)

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index f97e625..ff4a0bc 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -13,6 +13,7 @@
 #include <linux/eventfd.h>
 #include <linux/file.h>
 #include <linux/slab.h>
+#include <linux/export.h>
 #include "lg.h"
 
 /*L:056