net: page_pool: don't use page->private to store dma_addr_t

As pointed out by David Miller the current page_pool implementation
stores dma_addr_t in page->private.
This won't work on 32-bit platforms with 64-bit DMA addresses since the
page->private is an unsigned long and the dma_addr_t a u64.

A previous patch is adding dma_addr_t on struct page to accommodate this.
This patch adapts the page_pool related functions to use the newly added
struct for storing and retrieving DMA addresses from network drivers.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>