btrfs: ctree.h: Fix wrong comment position about csum size

Signed-off-by: NTomohiro Misono <misono.tomohiro@jp.fujitsu.com>
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -89,9 +89,9 @@ struct btrfs_ordered_sum;
  */
 #define BTRFS_LINK_MAX 65535U
 
+/* four bytes for CRC32 */
 static const int btrfs_csum_sizes[] = { 4 };
 
-/* four bytes for CRC32 */
 #define BTRFS_EMPTY_DIR_SIZE 0
 
 /* ioprio of readahead is set to idle */