ACPI video: check cap._DDC flag before getting EDID

cap._DDC is defined but never used.
Check this flag now and don't try to get EDID for video output devices with this flag cleared.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/video.c

@@ -1275,6 +1275,9 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id,
 		if (!video_device)
 			continue;
 
+		if (!video_device->cap._DDC)
+			continue;
+
 		if (type) {
 			switch (type) {
 			case ACPI_VIDEO_DISPLAY_CRT: