Fixed a consistency check in make_edi for flooding

Fixed a consistency check in make_edi for flooding

If one sets up a flooding .edi input file with gmx make_edi,
the code should check that one does not use of the last 6 eigenvectors
of the covariance matrix, which correspond to the rotational and
translational degrees of freedom.
The check that was in the code erroneously checked against the
number of eigenvalues neig that was stored in the .xvg file,
not against the total number of eigenvectors which depends on
the number of atoms nav used in gmx covar. Thus the original
check would always fail if the .xvg eigenvalue file contained
1-6 values only.

Change-Id: Ib293f6b69b80fbf014a7507431beaf1f939849ac