package/poppler: fix openjpeg support

Since the last version bump --enable-libopenjpeg always needs a
parameter:
https://cgit.freedesktop.org/poppler/poppler/commit/configure.ac?id=65c5a5266462244130f110599ac5d1011a04216e

Fixes
http://autobuild.buildroot.net/results/557/557b9b386863b6c865bcca86a2b87c7028700ec4/
http://autobuild.buildroot.net/results/f27/f27380e803be50e066be1659a8512fd74d1fa6de/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>