patches/openwrt: fix Permission denied warning

%: opkg install xinetd
//usr/lib/opkg/info/xinetd.postinst: line 261: /etc/init.d/: Permission denied

Reported in https://forum.turris.cz/t/postinst-script-permission-denied-for-etc-init-d/17473/4

I am not sure why this is happening yet, but this is a solution for now. It doesn't happen on my Turris MOX with TOS 6.0 and Turris Omnia (also with TOS 6.0), but does happen on my second Omnia with TOS 6.0 with the same opkg checksum as on the Omnia on which this works.