xtables-compat: ebtables: allow checking for zero-mac

xtables-compat: ebtables: allow checking for zero-mac

Allow checking for an all-zero mac address by replacing checks on the
address with a check on the option flag.

Its set when '-d' or '-s' appears on the command line and when seeing
a linklayer payload request for ether s/daddr.

Same for -p: s this flag gets removed during getopt when 'p' is encountered.

So, if its set, no need to check protocol type.

Signed-off-by: Florian Westphal <fw@strlen.de>