Wrap several common instances of:
	kmemdup(nla_data(attr), nla_len(attr), GFP_KERNEL);
Signed-off-by: NThomas Graf <tgraf@suug.ch>
Acked-by: NJohannes Berg <johannes@sipsolutions.net>
Acked-by: NDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>