repair: remove duplicate field from aghdr_cnts

repair: remove duplicate field from aghdr_cnts

The agicount and icount fields are used in separate parts of the AG scan
but both fields track the same data. agicount is used to compare with
the AGI header and icount is used to calculate the total inode count to
compare with sb_icount.

Use agicount rather than icount in scan_ags() and remove the icount
field.

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