board: rockchip: add support for Qnap TS433 devices

The Qnap TS433 is a 4-bay NAS based around the RK3568.

Two SATA bays are connected to the RK3568's own SATA controllers while
the other two are connected to a JMicron SATA controller living on the
PCIe bus.

It provides one 2.5Gb and one 1Gb ethernet port as well as 3 usb ports.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/doc/board/rockchip/rockchip.rst b/doc/board/rockchip/rockchip.rst
index 7b11a2e..0783603 100644
--- a/doc/board/rockchip/rockchip.rst
+++ b/doc/board/rockchip/rockchip.rst
@@ -119,6 +119,7 @@
      - FriendlyElec NanoPi R5S (nanopi-r5s-rk3568)
      - Generic RK3566/RK3568 (generic-rk3568)
      - Hardkernel ODROID-M1 (odroid-m1-rk3568)
+     - QNAP TS-433 (qnap-ts433-rk3568)
      - Radxa E25 Carrier Board (radxa-e25-rk3568)
      - Radxa ROCK 3A (rock-3a-rk3568)
      - Radxa ROCK 3B (rock-3b-rk3568)