hdl/ip_cores/general-cores: update submodule reference
hdl/ip_cores/dsp-cores: update submodule reference
hdl/top/afc_v3/*/dbe_bpm_dsp.ucf: add dsp-cores CE constraints

This eases the timing clousure
hdl/top/afc_v3/*/*.vhd: add MIXER to acquisition core

Also, as the dsp-cores position_calc_core has chanegd its
name, we updated it here.