fdt: Remove usage of string_builder module

The complex string_builder module in mosys is used trivially here for
a simple concatenation which can be done by the preprocessor.  This
allows us to remove the string_builder module (next CL).

BUG=none
TEST=compiles

Change-Id: I69d47fb61775bd3e2423050e4c4cc7a4ca815955
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/mosys/+/4958234
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
1 file changed