hdl/modules/wb_position_calc/*: add window path selection function

Now, the Window file is selected automatically depending on
the RFFE version passed
hdl/modules/dsp_cores_pkg.vhd: update module definitions

The generic definitions for the wb_position_calc_core.vhd and
xwb_position_calc_core.vhd are changed, so we update them in the
main DSP package
Merge branch 'slac-test-rffe_v1' into slac-test