enic: convert to SKB paged frag API.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Christian Benvenuti <benve@cisco.com>
Cc: Vasanthy Kolluri <vkolluri@cisco.com>
Cc: Roopa Prabhu <roprabhu@cisco.com>
Cc: David Wang <dwang2@cisco.com>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>