syslog-ng: Add a PACKAGECONFIG for syslog-ng-libs

This solves the following warning:
WARNING: QA Issue: syslog-ng-libs rdepends on geoip, but it isn't a build
dependency? [build-deps]

Signed-off-by: Chong Lu <Chong.Lu@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>