arm64: imx: imx8mp-debix-model-a: Migrate to OF_UPSTREAM

Device tree for this board can be deleted. Device tree location
now points to the freescale/ directory.

Use absolute path to PMIC node entry and its regulators as
device tree in kernel does not provide corresponding labels

Signed-off-by: Gilles Talis <gilles.talis@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
diff --git a/configs/imx8mp_debix_model_a_defconfig b/configs/imx8mp_debix_model_a_defconfig
index dcc529f..9f75ab1 100644
--- a/configs/imx8mp_debix_model_a_defconfig
+++ b/configs/imx8mp_debix_model_a_defconfig
@@ -8,7 +8,7 @@
 CONFIG_ENV_SIZE=0x1000
 CONFIG_ENV_OFFSET=0x400000
 CONFIG_DM_GPIO=y
-CONFIG_DEFAULT_DEVICE_TREE="imx8mp-debix-model-a"
+CONFIG_DEFAULT_DEVICE_TREE="freescale/imx8mp-debix-model-a"
 CONFIG_SPL_TEXT_BASE=0x920000
 CONFIG_TARGET_IMX8MP_DEBIX_MODEL_A=y
 CONFIG_SYS_MONITOR_LEN=524288