Newer Rockchip SoCs have more muxing slots.  Add slots 3 and 4 since
the rk3288 table goes all the way up to 4.
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>