tg3: Add extend rx ring sizes for 5717 and 5719

This patch increases the rx ring sizes for those asic revs that support
them.

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