xfs_mdrestore: fix missed progress reporting

xfs_mdrestore: fix missed progress reporting

Currently, the progress reporting only triggers when the number of bytes
read is exactly a multiple of a megabyte.  This isn't always guaranteed,
since AG headers can be 512 bytes in size.  Fix the algorithm by
recording the number of megabytes we've reported as being read, and emit
a new report any time the bytes_read count, once converted to megabytes,
doesn't match.

Fix the v2 code to emit one final status message in case the last
extent restored is more than a megabyte.

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