[NetLabel]: rework the Netlink attribute handling (part 2)

At the suggestion of Thomas Graf, rewrite NetLabel's use of Netlink attributes
to better follow the common Netlink attribute usage.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc net/netlabel/netlabel_cipso_v4.c
Simple merge

diff --cc net/netlabel/netlabel_cipso_v4.h
Simple merge

diff --cc net/netlabel/netlabel_mgmt.c
Simple merge

diff --cc net/netlabel/netlabel_mgmt.h
Simple merge

diff --cc net/netlabel/netlabel_unlabeled.c
Simple merge

diff --cc net/netlabel/netlabel_unlabeled.h
Simple merge