net: netlink_getname, packet_getname -- use DECLARE_SOCKADDR guard

Use guard DECLARE_SOCKADDR in a few more places which allow
us to catch if the structure copied back is too big.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>