s2ram: Added command line option -? (revert 1a6e6d9)

The -? command line option is used by getopt and getopt_long if the
option is not recognized. For more information, see getopt and
getopt_long manpages.

This commit reverts the previous commit 1a6e6d9 which removed this
option.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>