Fixed error reporting when you don't specify an input image.

One of the recent comments to update_firmware_vars.py made it
give bad error messages when you didn't specify an input image.
This restores the proper error message (and fixes some typos).

BUG=none
TEST=Ran update_firmware_vars.py with no args.
TEST=Ran update_firmware_vars.py with a bogus -i.
TEST=Ran update_firmware_vars.py --test

Change-Id: I4643cb382742f07f6db167f91d66364b4ebc8639
Reviewed-on: http://gerrit.chromium.org/gerrit/5511
Tested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Nick Sanders <nsanders@chromium.org>
1 file changed