dts: meson: Switch GXL, GXM & AXG to using upstream DT

Enable OF_UPSTREAM to use upstream DT and add amlogic/ prefix to the
DEFAULT_DEVICE_TREE. And thereby directly build DTB from dts/upstream/src/
including *-u-boot.dtsi files from arch/$(ARCH)/dts/ directory.

Cc: Sumit Garg <sumit.garg@linaro.org>
Acked-by: Viacheslav Bocharov <adeep@lexina.in>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> # khadas-vim3_android
Link: https://lore.kernel.org/r/20240329-u-boot-of-upstream-v2-2-2512ad3eb63d@linaro.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
diff --git a/configs/libretech-ac_defconfig b/configs/libretech-ac_defconfig
index f0ab195..6ad0457 100644
--- a/configs/libretech-ac_defconfig
+++ b/configs/libretech-ac_defconfig
@@ -9,7 +9,7 @@
 CONFIG_ENV_OFFSET=0xFFFF0000
 CONFIG_ENV_SECT_SIZE=0x10000
 CONFIG_DM_GPIO=y
-CONFIG_DEFAULT_DEVICE_TREE="meson-gxl-s805x-libretech-ac"
+CONFIG_DEFAULT_DEVICE_TREE="amlogic/meson-gxl-s805x-libretech-ac"
 CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_DM_RESET=y
 CONFIG_MESON_GXL=y