dm clone: drop redundant size checks

dm clone: drop redundant size checks

The clone target already exposes both source and destination devices via
clone_iterate_devices(), so dm-table's device_area_is_invalid() helper
ensures that the mapping does not extend past either underlying block
device.

The manual comparisons between ti->len and the source/destination device
sizes in parse_source_dev() and parse_dest_dev() are therefore
redundant. Remove these checks and rely on the core validation instead.
This changes the error strings reported when the devices are too small,
but preserves the failure behaviour.

Signed-off-by: Li Chen <me@linux.beauty>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>