bna: convert to SKB paged frag API.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Rasesh Mody <rmody@brocade.com>
Cc: Debashis Dutt <ddutt@brocade.com>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>