ixgbe: fix inconsistent SFP/SFP+ failure results.

Currently if we loaded the driver, insert an unsupported module, and then
attempt to "ifconfig up" the device it will be brought down but the netdev
would not be unregistered. This behavior is different than all other
code paths. This patch corrects that by down'ing the device and then
scheduling the sfp_config_module_task tasklet. The tasklet will detect
this condition (like it does with other code paths) and do the
unregister_netdev().

I also removed the log message as this condition (an unsupported SFP+
module) will be logged in sfp_config_module_task.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>