bnx2: use device model DMA API

Use DMA API as PCI equivalents will be deprecated. This change also allow
to allocate with GFP_KERNEL in some places.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>