netpoll: private skb pool (rev3)

It was a dark and stormy night when Steve first saw the
netpoll beast. The beast was odd, and misshapen but not
extremely ugly.

"Let me take off one of your warts" he said. This wart
is where you tried to make an skb list yourself. If the
beast had ever run out of memory, he would have stupefied
himself unnecessarily.

The first try was painful, so he tried again till the bleeding
stopped. And again, and again...

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>