Some GPUs will report a virtual edid even there is no monitor connected to

the VGA/HDMI port, when a monitor is plugged in, the edid will be updated. The old pattern is not working for some GPUs, because the edid is already in the cache with wrong data.

So we clear edid when output changed, to make libkscreen to get the latest edid and improve hardware compatibility.

Signed-off-by: likai likai@kylinos.cn