[PATCH 0/3]: Put DMA cookies into skb_shared_info().

In order to facilitate several things, including some software
GSO hacks Herbert and I want to do, these patches add DMA address
cookies into the SKB shared data area.

The first patch adjusts the datastructures.

The second one adds some DMA mapping helpers that drivers can
use.

The third patch converts tg3 as a proof of concept.