igb: remove duplicated #include

Remove duplicated #include('s) in
  drivers/net/igb/igb_main.c

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>