nla_total_size returns the total length of attribute
including padding.
Cc: Joe Stringer <joe@ovn.org> Cc: William Tu <u9012063@gmail.com> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com> Acked-by: Pravin B Shelar <pshelar@ovn.org> Signed-off-by: David S. Miller <davem@davemloft.net>