Remove some legacy MKL FFT code


git-svn-id: svn://svn.code.sf.net/p/cp2k/code/trunk@12792 bac0169d-1eea-4375-b5f6-f89d2ced9994
... and remove one further reference to a now deleted file


git-svn-id: svn://svn.code.sf.net/p/cp2k/code/trunk@12793 bac0169d-1eea-4375-b5f6-f89d2ced9994