xfs: Use defines for CRC offsets in all cases

Some calls to crc functions used useful #defines,
others used awkward offsetof() constructs.

Switch them all to #define to make things a bit cleaner.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_symlink_remote.c

@@ -134,7 +134,7 @@ xfs_symlink_read_verify(
 		return;
 
 	if (!xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length),
-				  offsetof(struct xfs_dsymlink_hdr, sl_crc)) ||
+				  XFS_SYMLINK_CRC_OFF) ||
 	    !xfs_symlink_verify(bp)) {
 		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
 		xfs_buf_ioerror(bp, EFSCORRUPTED);
@@ -162,8 +162,7 @@ xfs_symlink_write_verify(
 		struct xfs_dsymlink_hdr *dsl = bp->b_addr;
 		dsl->sl_lsn = cpu_to_be64(bip->bli_item.li_lsn);
 	}
-	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
-			 offsetof(struct xfs_dsymlink_hdr, sl_crc));
+	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length), XFS_SYMLINK_CRC_OFF);
 }
 
 const struct xfs_buf_ops xfs_symlink_buf_ops = {