If you feed the tool a suitable bogus register map you can break it
in arbitary (code executing) ways. While this isn't a particularly
exciting or probable attack vector we still ought to fix it.

One of a set of sscanf issues reported by Jackie Chang
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>