rockchip: dts: Clean up graffiti in rk3399-sdram-ddr3-1333.dtsi

The DDR3-1333 timings for the RK3399-Q7 (Puma) has some unintended
left-over comments in them. This change cleans the file up.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Simon Glass <sjg@chromium.org>