repair: validate ir_count field for sparse format records

repair: validate ir_count field for sparse format records

Sparse format inobt records contain an additional count field that
records the number of physical inodes tracked by the record. Verify the
count is internally consistent according to the holemask, similar to how
freecount is validated against the free mask.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>