scsi: target: fix PR IN / READ FULL STATUS for FC

scsi: target: fix PR IN / READ FULL STATUS for FC

Creation of the response to READ FULL STATUS fails for FC based
reservations. Reason is the too high loop limit (< 24) in
fc_get_pr_transport_id(). The string representation of FC WWPN is 23 chars
long only ("11:22:33:44:55:66:77:88"). So when i is 23, the loop body is
executed a last time for the ending '\0' of the string and thus hex2bin()
reports an error.

Link: https://lore.kernel.org/r/20200408132610.14623-3-bstroesser@ts.fujitsu.com
Signed-off-by: Bodo Stroesser <bstroesser@ts.fujitsu.com>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>