cifs: account for IPv6 in ses->serverName and clean up netbios name handling

The current code for setting the session serverName is IPv4-specific.
Allow it to be an IPv6 address as well. Use NIP* macros to set the
format.

This also entails increasing the length of the serverName field, so
declare a new macro for RFC1001 name length and use it in the
appropriate places.

Finally, drop the unicode_server_Name field from TCP_Server_Info since
it's not used. We can add it back later if needed, but for now it just
wastes memory.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>