Revert "qt-mobility: remove /usr/lib from ld rpath-link option"

* Basically part of the headers/libs are installed in
  ${D}(${libdir}/${includedir}) instead of
  ${D}(${libdir}/${includedir})/qt4

* http://lists.openembedded.org/pipermail/openembedded-core/2013-October/085815.html
  is related, but doesn't fix the issue completely, so better
  revert the commit which introduced this issue

This reverts commit f7409a9fe83ba2535a43f39ed57cd78242a88557.