ARM: dts: meson8b: odroidc1: enable the SDHC controller

Odroid-C1 has an eMMC connector where users can optionally install an
eMMC module. The eMMC modules run off a 1.8V VQMMC supply which means
that HS-200 mode can be used (this is the highest mode that the SDHC
controller supports). Enable the SDHC controller so eMMC modules can be
accessed.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20200620163654.37207-4-martin.blumenstingl@googlemail.com