arm64: dts: meson: g12a: add SDIO controller

The Amlogic G12A SDIO Controller has a bug preventing direct DDR access,
add the port A (SDIO) pinctrl and controller nodes and mark this specific
controller with the amlogic,dram-access-quirk property.

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