[GFS2] Use void * instead of typedef for locking module interface

As requested by Jan Engelhardt, this removes the typedefs in the
locking module interface and replaces them with void *. Also
since we are changing the interface, I've added a few consts
as well.

Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h
index e3bf4bc..52b8a30 100644
--- a/fs/gfs2/glock.h
+++ b/fs/gfs2/glock.h
@@ -140,7 +140,7 @@
 int gfs2_lvb_hold(struct gfs2_glock *gl);
 void gfs2_lvb_unhold(struct gfs2_glock *gl);
 
-void gfs2_glock_cb(struct gfs2_sbd *sdp, unsigned int type, void *data);
+void gfs2_glock_cb(void *cb_data, unsigned int type, void *data);
 
 void gfs2_iopen_go_callback(struct gfs2_glock *gl, unsigned int state);