ddc_add_display_by_businfo(): assign display number 1 higher than any…

… already used

was temporarily assigning dispno 99, which libddcutil used only to check
that display ref not invalid

src/ddc/ddc_displays.c

@@ -2026,7 +2026,7 @@ Display_Ref * ddc_add_display_by_businfo(I2C_Bus_Info * businfo) {
    if (businfo->edid) {
       dref = create_bus_display_ref(businfo->busno);
       // dref->dispno = DISPNO_INVALID;   // -1, guilty until proven innocent
-      dref->dispno = 99;   // dispno not used in libddcutil except to indicate invalid
+      dref->dispno = ++dispno_max;   // dispno not used in libddcutil except to indicate invalid
       dref->pedid = copy_parsed_edid(businfo->edid);
       dref->mmid  = mmk_new(
                        dref->pedid->mfg_id,