scsi_transport_iscsi: Add 25G and 40G speed definition

iscsi_port_speed and iscsi_port_speed_names have new entries for
25Gbps and 40Gbps link speeds.

Signed-off-by: Jitendra Bhivare <jitendra.bhivare@avagotech.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>