ARM64: dts: meson-gxl: libretech-cc: enable high speed modes

Enable sdcard UHS modes up to SDR50. Unfortunately, it seems the PCB of
the libretech-cc cannot handle SDR104 at 200Mhz reliably.
Also enable eMMC DDR52 mode.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>