Propagate the error code using return values instead, but let cli_classic.c
still decide the ultimate return value of the process.
Also, remove setting the ret value again after print_supported_wiki() - 
success is the default.

Corresponding to flashrom svn r1614.

Signed-off-by: Niklas Söderlund <niso@kth.se>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>