Use c_sdp_P_sum = 2, instead of c_dual.

...s/lofar2/libraries/sdp/src/vhdl/sdp_beamformer_remote.vhd

applications/lofar2/libraries/sdp/src/vhdl/sdp_pkg.vhd

applications/lofar2/libraries/sdp/src/vhdl/sdp_station.vhd