iptables: remove /etc/ethertypes

When building an image including iptable built with the libnftnl
PACKAGECONFIG, one hits

Downloading file:.../oe-rootfs-repo/armv8a/libkmod2 * check_data_file_clashes: Package iptables wants to install file .../rootfs/etc/ethertypes
        But that file is already provided by package  * netbase

This used to be handled by
0003-Makefile.am-do-not-install-etc-ethertypes.patch, but that patch
got removed with the 1.8.9->1.8.10 upgrade (commit 4616ada82e70).

I think the rationale for dropping the patch was wrong; the commit log
talks about xtables.conf, which is indeed gone from upstream, but said
patch didn't change anything about xtables.conf, it did

-dist_conf_DATA        = etc/ethertypes etc/xtables.conf
+dist_conf_DATA        = etc/xtables.conf

However, instead of patching iptables to not install ethertypes, and
having to forward-port that patch, it is much simpler to just remove
the file in this do_install:append.

(From OE-Core rev: a970b6c927fb4c04473484f6e4b0a9853c8a5896)

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-extended/iptables/iptables_1.8.10.bb

@@ -78,6 +78,8 @@ do_install:append() {
         ln -sf ${sbindir}/xtables-nft-multi ${D}${sbindir}/iptables 
         ln -sf ${sbindir}/xtables-nft-multi ${D}${sbindir}/iptables-save
         ln -sf ${sbindir}/xtables-nft-multi ${D}${sbindir}/iptables-restore
+        # ethertypes is provided by the netbase package
+        rm -f ${D}${sysconfdir}/ethertypes
     fi
 }