lockref: drop superfluous externs

Drop the superfluous externs from the remaining prototypes in lockref.h.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250115094702.504610-5-hch@lst.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Christoph Hellwig

include/linux/lockref.h

@@ -34,12 +34,12 @@ struct lockref {
 	};
 };
 
-extern void lockref_get(struct lockref *);
-extern int lockref_put_return(struct lockref *);
+void lockref_get(struct lockref *lockref);
+int lockref_put_return(struct lockref *lockref);
 bool lockref_get_not_zero(struct lockref *lockref);
 bool lockref_put_or_lock(struct lockref *lockref);
 
-extern void lockref_mark_dead(struct lockref *);
+void lockref_mark_dead(struct lockref *lockref);
 bool lockref_get_not_dead(struct lockref *lockref);
 
 /* Must be called under spinlock for reliable results */