board: rockchip: Add Radxa ZERO 3W/3E

The Radxa ZERO 3W/3E is an ultra-small, high-performance single board
computer based on the Rockchip RK3566, with a compact form factor and
rich interfaces.

Implement rk_board_late_init() to set correct fdtfile env var and
board_fit_config_name_match() to load correct FIT config based on what
board is detected at runtime so a single board target can be used for
both board models.

Features tested on a ZERO 3W 8GB v1.11:
- SD-card boot
- eMMC boot
- USB gadget
- USB host

Features tested on a ZERO 3E 4GB v1.2:
- SD-card boot
- Ethernet
- USB gadget
- USB host

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: FUKAUMI Naoki <naoki@radxa.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/doc/board/rockchip/rockchip.rst b/doc/board/rockchip/rockchip.rst
index 7115cfb..3febebd 100644
--- a/doc/board/rockchip/rockchip.rst
+++ b/doc/board/rockchip/rockchip.rst
@@ -107,6 +107,7 @@
      - Powkiddy X55 (powkiddy-x55-rk3566)
      - Radxa CM3 IO Board (radxa-cm3-io-rk3566)
      - Radxa ROCK 3C (rock-3c-rk3566)
+     - Radxa ZERO 3W/3E (radxa-zero-3-rk3566)
 
 * rk3568
      - Rockchip Evb-RK3568 (evb-rk3568)