vt: don't export vt_kmsg_redirect() to userspace

Fix following warning in linux-next by guarding the function definition
(both the "extern" and the inline) with #ifdef __KERNEL__.

usr/include/linux/vt.h:89: userspace cannot call function or variable defined in
the kernel

Introduced by commit 5ada918b82399eef3afd6a71e3637697d6bd719f ("vt:
introduce and use vt_kmsg_redirect() function").

Signed-off-by: Bernhard Walle <bernhard@bwalle.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/vt.h

@@ -84,6 +84,8 @@ struct vt_setactivate {
 
 #define VT_SETACTIVATE	0x560F	/* Activate and set the mode of a console */
 
+#ifdef __KERNEL__
+
 #ifdef CONFIG_VT_CONSOLE
 
 extern int vt_kmsg_redirect(int new);
@@ -97,6 +99,8 @@ static inline int vt_kmsg_redirect(int new)
 
 #endif
 
+#endif /* __KERNEL__ */
+
 #define vt_get_kmsg_redirect() vt_kmsg_redirect(-1)
 
 #endif /* _LINUX_VT_H */