net: dns: Parse individual labels in CNAME properly

The ANCOUNT has nothing to do with label count so remove the
original while loop and just go through all the labels until
we have read all of them.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>