arm64: dts: rockchip: add sdmmc card detect to the nanopc-t6

The nanopc-t6 has an sdmmc card detect connected to gpio0_a4 which is
active low.

Signed-off-by: John Clark <inindev@gmail.com>
Link: https://lore.kernel.org/r/20231230165053.3781-1-inindev@gmail.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>