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_dinode.h b/fs/xfs/xfs_dinode.h
index e5869b5..623bbe8 100644
--- a/fs/xfs/xfs_dinode.h
+++ b/fs/xfs/xfs_dinode.h
@@ -89,6 +89,8 @@
 	/* structure must be padded to 64 bit alignment */
 } xfs_dinode_t;
 
+#define XFS_DINODE_CRC_OFF	offsetof(struct xfs_dinode, di_crc)
+
 #define DI_MAX_FLUSH 0xffff
 
 /*