[SCSI] isci: Adding documentation to API change and fixup sysfs registration

Adding API update for adding isci_id entry scsi_host sysfs entry.
Also fixing up the sysfs registration to the scsi_host template

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>