pc-bios/s390-ccw: fix old bug in ptr increment

We need to increment by the size of the structure, whereas 'ns' is 'uint8_t *'.

Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Eugene (jno) Dvurechenski <jno@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

pc-bios/s390-ccw/bootmap.c

@@ -424,7 +424,7 @@ static void ipl_scsi(void)
     IPL_assert(magic_match(sec, ZIPL_MAGIC), "No zIPL magic");
 
     ns_end = sec + virtio_get_block_size();
-    for (ns = (sec + pte_len); (ns + pte_len) < ns_end; ns++) {
+    for (ns = (sec + pte_len); (ns + pte_len) < ns_end; ns += pte_len) {
         prog_table_entry = (ScsiBlockPtr *)ns;
         if (!prog_table_entry->blockno) {
             break;