selection.h: add tty_struct forward declaration

In file included from drivers/video/console/newport_con.c:16:
include/linux/selection.h:16: warning: "struct tty_struct" declared inside parameter list
include/linux/selection.h:16: warning: its scope is only this definition or declaration, which is probably not what you want

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/selection.h

@@ -10,6 +10,8 @@
 #include <linux/tiocl.h>
 #include <linux/vt_buffer.h>
 
+struct tty_struct;
+
 extern struct vc_data *sel_cons;
 
 extern void clear_selection(void);