cxgb: Use napi_alloc_skb instead of netdev_alloc_skb_ip_align

In order to use napi_alloc_skb I needed to pass a pointer to struct adapter
instead of struct pci_dev.  This allowed me to access &adapter->napi.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>