lenovo: Don't use extern with functions

Change-Id: I8313ba1d93922297e5061701dad47d07617d1dcd
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17804
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/mainboard/lenovo/t400/dock.h b/src/mainboard/lenovo/t400/dock.h
index ac6d81a..74b730c 100644
--- a/src/mainboard/lenovo/t400/dock.h
+++ b/src/mainboard/lenovo/t400/dock.h
@@ -16,7 +16,7 @@
 #ifndef THINKPAD_T400_DOCK_H
 #define THINKPAD_T400_DOCK_H
 
-extern void dock_connect(void);
-extern void dock_disconnect(void);
-extern int dock_present(void);
+void dock_connect(void);
+void dock_disconnect(void);
+int dock_present(void);
 #endif