clk: rockchip: fix the rk3399 sdmmc sample / drv name

The rk3399 clock table had a simple typo in it, calling the SDMMC sample
and drive clocks by the wrong name.  Fix this minor typo.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Acked-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>