xfs_attr_leaf: use swap macro in xfs_attr3_leaf_rebalance

Make use of the swap macro and remove some unnecessary variables.
This makes the code easier to read and maintain. Also, reduces the
stack usage.

This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_attr_leaf.c

@@ -1566,17 +1566,10 @@ xfs_attr3_leaf_rebalance(
 	 */
 	swap = 0;
 	if (xfs_attr3_leaf_order(blk1->bp, &ichdr1, blk2->bp, &ichdr2)) {
-		struct xfs_da_state_blk	*tmp_blk;
-		struct xfs_attr3_icleaf_hdr tmp_ichdr;
+		swap(blk1, blk2);
 
-		tmp_blk = blk1;
-		blk1 = blk2;
-		blk2 = tmp_blk;
-
-		/* struct copies to swap them rather than reconverting */
-		tmp_ichdr = ichdr1;
-		ichdr1 = ichdr2;
-		ichdr2 = tmp_ichdr;
+		/* swap structures rather than reconverting them */
+		swap(ichdr1, ichdr2);
 
 		leaf1 = blk1->bp->b_addr;
 		leaf2 = blk2->bp->b_addr;