Staging: batman-adv: Prepare vis packets directly inside a skb

The vis information structure is used in a way that it can be transfered
directly as packet. It still had to be copied into a skb because of an
extra buffer used for the actual preparation of the data. This is
unnecessary and can be replaced by a simple clone instead of an full
copy before each send.

This makes also the send_raw_packet function obsolete.

Reported-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>