Fix this by wrapping the inet6 calls in #ifdef IPV6. Also make the
ocrdma module depend on (IPV6 || IPV6=n) to forbid the case of modular
ipv6 but built-in ocrdma (which can't work, because ocrdma calls ipv6
functions).
Reported-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Roland Dreier <roland@purestorage.com>