scsi: documentation: Document Fibre Channel sysfs node for appid

Update documentation for sysfs node within /sys/class/fc/fc_udev_device/.

Link: https://lore.kernel.org/r/20210913015853.2086512-1-muneendra.kumar@broadcom.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Muneendra Kumar <muneendra.kumar@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>