Remove PED_ASSERT from dos geometry checking

Remove PED_ASSERT from dos geometry checking

The CHS geometry values are calculated based on the existing partition
information. The values can't always be calculated, and the partition
may be corrupt so instead of throwing an assertion just return 0 and
carry on.

I left the logic for the PED_ASSERT checks the same so that it is clear
that the logic has not changed, it just returns 0 now.

* libparted/labels/dos.c (probe_partition_for_geom): remove PED_ASSERT