drm/panel: ilitek-ili9881c: Report subpixel order according to rotation

Assume a default RGB subpixel order and flip it around if 180° rotation
is configured via address mode. Report subpixel order to userspace.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240626-drm-panel-ili9881c-rotation-v1-2-e0ff54173e32@pengutronix.de
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240626-drm-panel-ili9881c-rotation-v1-2-e0ff54173e32@pengutronix.de

drivers/gpu/drm/panel/panel-ilitek-ili9881c.c

@@ -1471,6 +1471,10 @@ static int ili9881c_get_modes(struct drm_panel *panel,
 
 	connector->display_info.width_mm = mode->width_mm;
 	connector->display_info.height_mm = mode->height_mm;
+	if (ctx->address_mode == 0x3)
+		connector->display_info.subpixel_order = SubPixelHorizontalBGR;
+	else
+		connector->display_info.subpixel_order = SubPixelHorizontalRGB;
 
 	/*
 	 * TODO: Remove once all drm drivers call