Support applying SI per signal input.

...far2_unb2b_sdp_station/lofar2_unb2b_sdp_station.fpga.yaml

...far2_unb2c_sdp_station/lofar2_unb2c_sdp_station.fpga.yaml

libraries/dsp/si/si.peripheral.yaml

libraries/dsp/si/src/vhdl/si_arr.vhd