arm64: dts: rockchip: remove unsupported property from sdmmc2 for rock-3a

'supports-sdio' is not part of the DT binding
and not supported by the Linux driver.

Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://lore.kernel.org/r/20221219101052.7899-1-amadeus@jmu.edu.cn
Signed-off-by: Heiko Stuebner <heiko@sntech.de>