printk: export console_drivers

this symbol is needed by drivers/video/xen-fbfront.ko.

[ cherry-picked from tip/core/printk ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/printk.c b/kernel/printk.c
index 028ed75..1fb1382 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -75,6 +75,8 @@
 static DECLARE_MUTEX(console_sem);
 static DECLARE_MUTEX(secondary_console_sem);
 struct console *console_drivers;
+EXPORT_SYMBOL_GPL(console_drivers);
+
 /*
  * This is used for debugging the mess that is the VT code by
  * keeping track if we have the console semaphore held. It's