[GFS2] Remove unneeded i_spin

This patch removes a vestigial variable "i_spin" from the gfs2_inode
structure.  This not only saves us memory (>300000 of these in memory
for the oom test) it also saves us time because we don't have to
spend time initializing it (i.e. slightly better performance).
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/incore.h

@@ -267,7 +267,6 @@ struct gfs2_inode {
 	struct gfs2_alloc *i_alloc;
 	u64 i_last_rg_alloc;
 
-	spinlock_t i_spin;
 	struct rw_semaphore i_rw_mutex;
 };
 

fs/gfs2/main.c

@@ -29,7 +29,6 @@ static void gfs2_init_inode_once(struct kmem_cache *cachep, void *foo)
 	struct gfs2_inode *ip = foo;
 
 	inode_init_once(&ip->i_inode);
-	spin_lock_init(&ip->i_spin);
 	init_rwsem(&ip->i_rw_mutex);
 	ip->i_alloc = NULL;
 }