igb: output register's information related to RX/TX queue[4-15]

Current igb outputs registers related to TX/RX queues(ex. RDT, RDH, TDT, TDH).
But it thinks the number of RX/TX queues is 4. But 82576 has 16 RX/TX queues.
This patch modifies igb to output the rest of the registers if the device is
82576.

Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
Acked-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>