util/amdfwtool: unify return values, verify the file open

- Return an error if the specified file could not be opened. To do this
cleanly, the return value was added.
- Since there's now a unified return value, use it where it makes sense.
- Don't return an error from --help.  If you've asked for usage, it's
not an error.

Change-Id: I7c712d1e1927c2d4957b044b87ad26475b7a0e3b
Signed-off-by: Martin Roth <martinroth@chromium.org>
Reviewed-on: https://review.coreboot.org/17324
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc@marcjonesconsulting.com>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

0 files changed, 0 insertions, 0 deletions