scsi: fc: Add 256GBit speed setting to SCSI FC transport

Add 256GBit speed setting to the SCSI FC transport.  This speed can be
reached via FC trunking techniques.

Link: https://lore.kernel.org/r/20200831213518.48409-1-james.smart@broadcom.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>