xfs_repair: Add support for upgrading to large extent counters

This commit adds support to xfs_repair to allow upgrading an existing
filesystem to support per-inode large extent counters.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>