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>

diff --git a/fs/xfs/xfs_inode_buf.c b/fs/xfs/xfs_inode_buf.c
index 4fc9f39..606b43a 100644
--- a/fs/xfs/xfs_inode_buf.c
+++ b/fs/xfs/xfs_inode_buf.c
@@ -306,7 +306,7 @@
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return false;
 	if (!xfs_verify_cksum((char *)dip, mp->m_sb.sb_inodesize,
-			      offsetof(struct xfs_dinode, di_crc)))
+			      XFS_DINODE_CRC_OFF))
 		return false;
 	if (be64_to_cpu(dip->di_ino) != ip->i_ino)
 		return false;
@@ -327,7 +327,7 @@
 
 	ASSERT(xfs_sb_version_hascrc(&mp->m_sb));
 	crc = xfs_start_cksum((char *)dip, mp->m_sb.sb_inodesize,
-			      offsetof(struct xfs_dinode, di_crc));
+			      XFS_DINODE_CRC_OFF);
 	dip->di_crc = xfs_end_cksum(crc);
 }