The 5719 has bug where RDMAs larger than 4k can cause problems.  This
patch works around the problem by dividing larger DMA requests into
something the hardware can handle.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>