scsi: fcoe: Suppress a compiler warning

Suppress the following compiler warning:

warning: cast to smaller integer type
      'enum fip_mode' from 'void *' [-Wvoid-pointer-to-enum-cast]
        enum fip_mode fip_mode = (enum fip_mode)kp->arg;
                                 ^~~~~~~~~~~~~~~~~~~~~~

Link: https://lore.kernel.org/r/20210415220826.29438-9-bvanassche@acm.org


Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>