[U-Boot] [PATCH 52/53] binman: Correct the error message for invalid path

[sjg at google.com]

At present this message references -o for output file. But binman uses -f
now. Fix it.

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

 tools/binman/control.py | 4 ++--
 tools/binman/ftest.py   | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

Applied to u-boot-dm, thanks!