iop: ssh_upgrade: Disable host key checking

This change simplifies ssh updates when connecting to
different hosts with same IP address.

iop/scripts/iopupgrade.sh

@@ -274,6 +274,7 @@ function ssh_upgrade {
 	pv "$upd_fw" |
 		ssh \
 			-o ConnectTimeout=60 \
+			-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
 			root@"$upd_host" \
 			sh -c "cat > '/tmp/$upd_fw_base' && (set -x && sysupgrade -v $extra_args /tmp/$upd_fw_base)" ||
 		echo "Sysupgrade failed" >&2 && return 1