i40e: Missing response checks in driver when starting/stopping FW LLDP

Driver did not check response on LLDP flag change and always returned
SUCCESS.

This patch now checks for an error and returns an error code and has
additional information in the log.

Signed-off-by: Piotr Marczak <piotr.marczak@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>