Define extra WPFB generics in t_wpfb_extra.

libraries/dsp/wpfb/src/vhdl/wpfb_pkg.vhd

libraries/dsp/wpfb/src/vhdl/wpfb_unit_dev.vhd

libraries/dsp/wpfb/tb/vhdl/tb_wpfb_unit_dev_wg.vhd