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/[e-mail]
Cc: Hannes Reinecke <[e-mail]>
Signed-off-by: Bart Van Assche <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/fcoe/fcoe_transport.c

···
 	int rc = -ENODEV;
 	struct net_device *netdev = NULL;
 	struct fcoe_transport *ft = NULL;
-	enum fip_mode fip_mode = (enum fip_mode)kp->arg;
+	enum fip_mode fip_mode = (enum fip_mode)(uintptr_t)kp->arg;
 
 	mutex_lock(&ft_mutex);