confd: Make physical port detection compatible with Linux 6.1

The old assumption was that only virtual links would have specific
"linkinfo" data. However, somewhere between 5.19 and 6.1, DSA ports
gained the ability to report its "conduit" interface via the
"linkinfo" attribute. That's great, but unfortunately it broke our
heuristic assumptions.

The new assumption is that only physical ports will report a
"parentbus" attribute. Let's see how long that will last :)

board/netconf/rootfs/lib/infix/factory/gen-interfaces

@@ -19,7 +19,7 @@ phys_ifaces=$(ip -d -j link show | jq -r '
 	 .[] |
 	 select(.link_type == "ether") |
 	 select(.group != "internal")  |
-	 select(has("linkinfo") | not) |
+	 select(has("parentbus")) |
 	 .ifname')
 
 cat <<EOF

src/confd/src/ietf-interfaces.c

@@ -50,7 +50,7 @@ static bool iface_is_phys(const char *ifname)
 	if (strcmp(attr, "ether"))
 		goto out_free;
 
-	if (!json_unpack(link, "[{s: { s:s }}]", "linkinfo", "info_kind", &attr))
+	if (json_unpack(link, "[{s:s}]", "parentbus", &attr))
 		goto out_free;
 
 	is_phys = true;