netlabel: return msg overflow error from netlbl_cipsov4_list faster

Currently, we are trying to place the information from the kernel to
1, 2, 3 and 4 pages sequentially. These pages are allocated via slab.
Though, from the slab point of view steps 3 and 4 are equivalent on
most architectures. So, lets skip 3 pages attempt.

By the way, should we switch from .doit to .dumpit interface here?
The amount of data seems quite big for me.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>