rockchip: Update todo in README.rockchip

MMC support works now, so it can be dropped from the todo

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
1 file changed