imx: imx8mm_evk: convert to OF_UPSTREAM

Convert i.MX8MM EVK to OF_UPSTREAM

Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/configs/imx8mm_evk_fspi_defconfig b/configs/imx8mm_evk_fspi_defconfig
index 34e8071..3aaf7a4 100644
--- a/configs/imx8mm_evk_fspi_defconfig
+++ b/configs/imx8mm_evk_fspi_defconfig
@@ -11,7 +11,7 @@
 CONFIG_ENV_OFFSET=0x400000
 CONFIG_IMX_CONFIG="board/freescale/imx8mm_evk/imximage-8mm-lpddr4-fspi.cfg"
 CONFIG_DM_GPIO=y
-CONFIG_DEFAULT_DEVICE_TREE="imx8mm-evk"
+CONFIG_DEFAULT_DEVICE_TREE="freescale/imx8mm-evk"
 CONFIG_SPL_TEXT_BASE=0x7E2000
 CONFIG_TARGET_IMX8MM_EVK=y
 CONFIG_SYS_MONITOR_LEN=524288