drm/nouveau: we can't free ACPI EDID, so make a copy that we can

The rest of the connector code assumes we can kfree() the EDID pointer.
This causes things to blow up with the ACPI EDID pointer we get
passed.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -292,6 +292,6 @@ nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector)
 	if (ret < 0)
 		return ret;
 
-	nv_connector->edid = edid;
+	nv_connector->edid = kmemdup(edid, EDID_LENGTH, GFP_KERNEL);
 	return 0;
 }