xfs_repair: support more than INT_MAX block maps

xfs_repair: support more than INT_MAX block maps

Now that it's possible to have more than INT_MAX block mappings attached
to a file fork, expand the counters used by this data structure so that
it can support all possible block mappings.

Note that in practice we're still never going to exceed 4 billion
extents because the previous patch switched off the block mappings for
regular files.  This is still twice as much as memory as previous, but
it's not totally unconstrained.  Hopefully few people bloat the xattr
structures that large.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>