cmdline: use new ethernet address parser

cmdline: use new ethernet address parser

Now that there is a version of ether_aton in rte_ether, it can
be used by the cmdline ethernet address parser.

Note: ether_aton_r can not be used in cmdline because
the old code would accept either bytes XX:XX:XX:XX:XX:XX
or words XXXX:XXXX:XXXX and we need to keep compatibility.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Olivier Matz <olivier.matz@6wind.com>