fdt: fix out of tree builds with DT support

Fix: FATAL ERROR: Couldn't open "../arch/arm/dts/tegra20.dtsi": No
such file or directory

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
1 file changed