tty: Add export.h for EXPORT_SYMBOL/THIS_MODULE to exporters

With module.h being implicitly everywhere via device.h, the absence
of explicitly including something for EXPORT_SYMBOL went unnoticed.
Since we are heading to fix things up and clean module.h from the
device.h file, we need to explicitly include these files now.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index 66825c9..7a367ff 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -22,6 +22,7 @@
 #include <linux/kernel.h>
 #include <linux/major.h>
 #include <linux/errno.h>
+#include <linux/export.h>
 #include <linux/tty.h>
 #include <linux/interrupt.h>
 #include <linux/mm.h>