This patch adds the hotplug unsol event handling to simple_hdmi*().
It works on VIA VX900.  If AMD or Nvidia chips support the
pin-detection similarly, it can be added easily, too.
Reported-by: NAnnie Liu <annieliu@viatech.com.cn>
Tested-by: NAnnie Liu <annieliu@viatech.com.cn>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>