link-config: make initialization to -1 less weird

memset() is weird anyway, since it expects an "int" as second parameter,
which it then uses as a byte, i.e. as uint8_t or something like that.
But by passing -1 to it, things get particularly weird, as that relies
on sign expansion to do the right thing.

src/udev/net/link-config.c

@@ -171,7 +171,7 @@ static int load_link(link_config_ctx *ctx, const char *filename) {
         link->port = _NET_DEV_PORT_INVALID;
         link->autonegotiation = -1;
 
-        memset(&link->features, -1, sizeof(link->features));
+        memset(&link->features, 0xFF, sizeof(link->features));
 
         r = config_parse(NULL, filename, file,
                          "Match\0Link\0Ethernet\0",