arm64: dts: rockchip: assign a fixed index to mmc devices on rk3328 boards

arm64: dts: rockchip: assign a fixed index to mmc devices on rk3328 boards

Recently introduced async probe on mmc devices can shuffle block IDs.
Pin them to fixed values to ease booting in environments where UUIDs
are not practical. Use newly introduced aliases for mmcblk devices from [1].

[1] https://patchwork.kernel.org/patch/11747669/

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20201219210500.3855-1-jbx6244@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>