pico-imx7d: Allow default fdtfile to be overridden by defconfig

This allow the addition of extra default configurations for each
baseboard, removing the boot menu when user boots for the first time.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
diff --git a/include/configs/pico-imx7d.h b/include/configs/pico-imx7d.h
index 8f1876c..13e7353 100644
--- a/include/configs/pico-imx7d.h
+++ b/include/configs/pico-imx7d.h
@@ -65,7 +65,7 @@
 	"console=ttymxc4\0" \
 	"fdt_high=0xffffffff\0" \
 	"initrd_high=0xffffffff\0" \
-	"fdtfile=ask\0" \
+	"fdtfile=" CONFIG_DEFAULT_FDT_FILE "\0" \
 	BOOTMENU_ENV \
 	"fdt_addr=0x83000000\0" \
 	"fdt_addr_r=0x83000000\0" \