tty: Correct inline types for tty_driver_kref_get()

tty_driver_kref_get() should be static inline and not extern inline
(the latter even changed it's semantics in gcc >= 4.3).
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/tty_driver.h

@@ -309,7 +309,8 @@ extern void tty_set_operations(struct tty_driver *driver,
 extern struct tty_driver *tty_find_polling_driver(char *name, int *line);
 
 extern void tty_driver_kref_put(struct tty_driver *driver);
-extern inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
+
+static inline struct tty_driver *tty_driver_kref_get(struct tty_driver *d)
 {
 	kref_get(&d->kref);
 	return d;