README.md: Add Rockchip RK322X description
README.md: Add Rockchip RK322X description

Signed-off-by: Joseph Chen <80c6ec8323b5b397c988e3ebe83c48154c3f18db@rock-chips.com>
Acked-by: Jerome Forissier <ced78d268b4c9a0a20a59a9feeebd2ad90da03d3@linaro.org>

pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os,pascal-brand-st-dev/optee_os