xfs: mute some sparse warnings

These three warnings are fixed:

fs/xfs/xfs_inode.c:1033:44: warning: Using plain integer as NULL pointer
fs/xfs/xfs_inode_item.c:525:20: warning: context imbalance in 'xfs_inode_item_push' - unexpected unlock
fs/xfs/xfs_dquot.c:696:1: warning: symbol 'xfs_dq_get_next_id' was not declared. Should it be static?

Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_dquot.c

@@ -692,7 +692,7 @@ error0:
  * end of the chunk, skip ahead to first id in next allocated chunk
  * using the SEEK_DATA interface.
  */
-int
+static int
 xfs_dq_get_next_id(
 	xfs_mount_t		*mp,
 	uint			type,

fs/xfs/xfs_inode.c

@@ -1030,7 +1030,7 @@ xfs_dir_ialloc(
 			tp->t_flags &= ~(XFS_TRANS_DQ_DIRTY);
 		}
 
-		code = xfs_trans_roll(&tp, 0);
+		code = xfs_trans_roll(&tp, NULL);
 		if (committed != NULL)
 			*committed = 1;
 

fs/xfs/xfs_inode_item.c

@@ -479,6 +479,8 @@ STATIC uint
 xfs_inode_item_push(
 	struct xfs_log_item	*lip,
 	struct list_head	*buffer_list)
+		__releases(&lip->li_ailp->xa_lock)
+		__acquires(&lip->li_ailp->xa_lock)
 {
 	struct xfs_inode_log_item *iip = INODE_ITEM(lip);
 	struct xfs_inode	*ip = iip->ili_inode;