major issue in NP folding for wind prescribed on geographical grid

This bug is similar to https://forge.ipsl.jussieu.fr/nemo/ticket/660 When using wind prescribed on geographical grid, the NP folding must have a sign +1 and not -1 as the wind with geographical orientation does not change sign on each side of the folding. The change of sign concerns only winds which direction corresponds to the grid. For geographical oriented wind, the change of sign will be done "automatically" when rotating the winds as the angle used for the rotation where defined with a -1 in their call to lnc_lnk. => bugfix : fix the sign of the sign that will be used by the lnb_lnk in fldread according to the need of a rotation.