datapath: Use proper buffer size in nla_memcpy

datapath: Use proper buffer size in nla_memcpy

Upstream commit:
    commit ac71b46efd2838c02ec193987c8f61c3ba33b495
    Author: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
    Date:   Mon Mar 28 18:08:59 2016 +0800

    openvswitch: Use proper buffer size in nla_memcpy

    For the input parameter count, it's better to use the size
    of destination buffer size, as nla_memcpy would take into
    account the length of the source netlink attribute when
    a data is copied from an attribute.

    Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Fixes: c5f6c06b58d6 ("datapath: Interface with NAT.")
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Jesse Gross <jesse@kernel.org>