util-linux: tweak sscanf-no-ms-as patch

The patch has a minor mistake so fix it.
Credit go to Daniel Mentz <daniel@exxm.de> for the detailed bug report.
Closes bug #6428

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>