package/util-linux: fix typo in configure.ac

Fixes:
http://autobuild.buildroot.net/results/993/9935cd0522d4f978ba2e788a690f66790686b76b



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Lada Trimasova <ltrimas@synopsys.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>