p0fem.hh: fix problem that arose during make headercheck,

DUNE_DEPRECATED_MSG at wrong position
made by Bernd, reviewed by Beatrix


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@14510 2fb0f335-1f38-0410-981e-8018bf24f1b0