qed: enhanced per queue max coalesce value.

Maximum coalesce per Rx/Tx queue is extended from
255 to 511.

Signed-off-by: Rahul Verma <rahul.verma@cavium.com>
Signed-off-by: Yuval Mintz <yuval.mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>