warp7: Convert to OF_UPSTREAM

Instead of using the local imx7s-warp devicetree copies from U-Boot,
convert the imx7s-warp board to OF_UPSTREAM so that the upstream
kernel devicetree can be used instead.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
diff --git a/configs/warp7_bl33_defconfig b/configs/warp7_bl33_defconfig
index 51e5200..6b68681 100644
--- a/configs/warp7_bl33_defconfig
+++ b/configs/warp7_bl33_defconfig
@@ -4,7 +4,7 @@
 CONFIG_ENV_SIZE=0x2000
 CONFIG_ENV_OFFSET=0x80000
 CONFIG_DM_GPIO=y
-CONFIG_DEFAULT_DEVICE_TREE="imx7s-warp"
+CONFIG_DEFAULT_DEVICE_TREE="nxp/imx/imx7s-warp"
 CONFIG_TARGET_WARP7=y
 CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_ARMV7_BOOT_SEC_DEFAULT=y