xfs_repair: fix bogosity when rmapping new AGFL blocks

xfs_repair: fix bogosity when rmapping new AGFL blocks

When repair rebuilds the AGFL, the blocks can come either from the
in-core free space tree or they can come as a result of overestimating
the number of blocks needed to rebuild the on-disk free space btree.
The code in here was trying to only create rmap records for AGFL blocks
that did /not/ come from free space btree rebuild overestimation, but
was totally broken.  The initial and check conditions were totally wrong
if there was any overflow.  Remove a stray debug printf too.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>