This function returns an error code and its caller may be able to fix the
error. For example fit_handle_file() expands the device tree to fit if there
is a lack of space.

In this case the caller does not want an error displayed. It is confusing,
since it suggests that something is wrong, when it fact everything is fine.
Drop the error.

Signed-off-by: Simon Glass <sjg@chromium.org>