drm/i915/sdvo: Handle unsupported GET_SUPPORTED_ENHANCEMENTS gracefully

In the event that the external chipset doesn't implement the
GET_SUPPORTED_ENHANCEMENTS commands, gracefully treat it as having no
enhancments rather than bailing.

Reported-and-tested-by: Woody Suwalski <terraluna977@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=18342
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_sdvo.c

@@ -2520,11 +2520,10 @@ static bool intel_sdvo_create_enhance_property(struct intel_sdvo *intel_sdvo,
 		uint16_t response;
 	} enhancements;
 
-	if (!intel_sdvo_get_value(intel_sdvo,
-				  SDVO_CMD_GET_SUPPORTED_ENHANCEMENTS,
-				  &enhancements, sizeof(enhancements)))
-		return false;
-
+	enhancements.response = 0;
+	intel_sdvo_get_value(intel_sdvo,
+			     SDVO_CMD_GET_SUPPORTED_ENHANCEMENTS,
+			     &enhancements, sizeof(enhancements));
 	if (enhancements.response == 0) {
 		DRM_DEBUG_KMS("No enhancement is supported\n");
 		return true;