This patch modifies the throughput mode poll settings to reduce the 
number of interrupts. This is only used by older hardware that need a 
timer irq in throughput mode.

Secondly, this patch increases the default rx ring from 128 to 512. This 
drastically improves bandwidth utilization for small packets sizes i.e 
512 bytes.

Signed-off-by: Ayaz Abdulla <aabdulla@nvidia.com>