rockchip: rk3288: provide ${fdtfile}

All rk3288 default configs define CONFIG_DEFAULT_DEVICE_TREE.
So we can use it to define ${fdtfile} in rk3288_common.h.

This variable is needed by the distro boot command.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

include/configs/rk3288_common.h

@@ -73,6 +73,7 @@
 #define CONFIG_EXTRA_ENV_SETTINGS \
 	"fdt_high=0x0fffffff\0" \
 	"initrd_high=0x0fffffff\0" \
+	"fdtfile=" CONFIG_DEFAULT_DEVICE_TREE ".dtb\0" \
 	"partitions=" PARTS_DEFAULT \
 	ENV_MEM_LAYOUT_SETTINGS \
 	ROCKCHIP_DEVICE_SETTINGS \