[GFS2] Remove unused go_callback operation

This is never used, so we might as well remove it.
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>

fs/gfs2/glock.c

@@ -1568,8 +1568,6 @@ static void blocking_cb(struct gfs2_sbd *sdp, struct lm_lockname *name,
 	if (!gl)
 		return;
 
-	if (gl->gl_ops->go_callback)
-		gl->gl_ops->go_callback(gl, state);
 	handle_callback(gl, state);
 
 	spin_lock(&gl->gl_spin);

fs/gfs2/incore.h

@@ -110,7 +110,6 @@ struct gfs2_glock_operations {
 	int (*go_demote_ok) (struct gfs2_glock *gl);
 	int (*go_lock) (struct gfs2_holder *gh);
 	void (*go_unlock) (struct gfs2_holder *gh);
-	void (*go_callback) (struct gfs2_glock *gl, unsigned int state);
 	const int go_type;
 };