netlink: add NLA_PUT_BE64 macro

Add NLA_PUT_BE64 macro required for 64bit counters in netfilter

Signed-off-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>