gfs2: Fix inode_go_instantiate description

Fixes a "function parameter or member gl not described in
inode_go_instantiate" warning.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glops.c

@@ -494,7 +494,7 @@ int gfs2_inode_refresh(struct gfs2_inode *ip)
 
 /**
  * inode_go_instantiate - read in an inode if necessary
- * @gh: The glock holder
+ * @gl: The glock
  *
  * Returns: errno
  */