drm/panel: otm8009a: Set backlight parent to panel device

This is the logical place to put the backlight device, and it also
fixes a kernel crash if the MIPI host is removed. Previously the
backlight device would be unregistered twice when this happened - once
as a child of the MIPI host through `mipi_dsi_host_unregister`, and
once when the panel device is destroyed.

Fixes: 12a6cbd4 ("drm/panel: otm8009a: Use new backlight API")
Signed-off-by: James Cowgill <james.cowgill@blaize.com>
Cc: stable@vger.kernel.org
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230412173450.199592-1-james.cowgill@blaize.com

drivers/gpu/drm/panel/panel-orisetech-otm8009a.c

@@ -471,7 +471,7 @@ static int otm8009a_probe(struct mipi_dsi_device *dsi)
 		       DRM_MODE_CONNECTOR_DSI);
 
 	ctx->bl_dev = devm_backlight_device_register(dev, dev_name(dev),
-						     dsi->host->dev, ctx,
+						     dev, ctx,
 						     &otm8009a_backlight_ops,
 						     NULL);
 	if (IS_ERR(ctx->bl_dev)) {