arm64: dts: rockchip: add ROCK Pi S DTS support

ROCK Pi S is RK3308 based SBC from radxa.com. ROCK Pi S has a,
- 256MB/512MB DDR3 RAM
- SD, NAND flash (optional on board 1/2/4/8Gb)
- 100MB ethernet, PoE (optional)
- Onboard 802.11 b/g/n wifi + Bluetooth 4.0 Module
- USB2.0 Type-A HOST x1
- USB3.0 Type-C OTG x1
- 26-pin expansion header
- USB Type-C DC 5V Power Supply

This patch enables
- Console
- NAND Flash
- SD Card

Signed-off-by: Akash Gajjar <akash@openedev.com>
[sjoerd: Sort dt nodes, drop properties duplicated from dtsi]
Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>
Link: https://lore.kernel.org/r/20220614064858.1445817-3-sjoerd@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>