[SCSI] scsi_transport_fc: Getting FC Port Speed in sync with FC-GS

The values for the 4G and 10G speeds are not in sync with
definitions in SM-HBA/FC-GS-x/etc.
This patch brings them in sync to these specifications.

The values are converted to strings when represented via
sysfs attribute, hence that should cover for user space
apps as they may not see any change.

Signed-off-by: Neerav Parikh <neerav.parikh@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Acked-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>