rockchip: fix SUPPORTED_DEVICES for Radxa ROCK Pi 4

This sets SUPPORTED_DEVICES to match the compatible in the DTS.

While at it, synchronize the capitalization in DEVICE_MODEL and
DTS model.

Signed-off-by: Marty Jones <[email protected]>
[commit title/message facelift, move variable in armv8.mk]
Signed-off-by: Adrian Schmutzler <[email protected]>

target/linux/rockchip/image/armv8.mk

@@ -26,8 +26,9 @@ TARGET_DEVICES += pine64_rockpro64
 
 define Device/radxa_rock-pi-4
   DEVICE_VENDOR := Radxa
-  DEVICE_MODEL := Rock Pi 4
+  DEVICE_MODEL := ROCK Pi 4
   SOC := rk3399
+  SUPPORTED_DEVICES := radxa,rockpi4
   UBOOT_DEVICE_NAME := rock-pi-4-rk3399
   IMAGE/sysupgrade.img.gz := boot-common | boot-script | pine64-img | gzip | append-metadata
 endef