modem|psk: cleaning up internal modulate method
modem|psk: cleaning up internal modulate method

  * using internal liquid_cexpjf() method for rotation rather
    than lmath's cexpf()
  * still using mapping for faster computation

biotrump/liquid-dsp,wangning223/liquid-dsp,manuts/liquid-dsp,biotrump/liquid-dsp,jgaeddert/liquid-dsp,JayKickliter/liquid-dsp,cjcliffe/liquid-dsp,jgaeddert/liquid-dsp,biotrump/liquid-dsp,wangning223/liquid-dsp,wangning223/liquid-dsp,manuts/liquid-dsp,manuts/liquid-dsp,biotrump/liquid-dsp,jgaeddert/liquid-dsp,wangning223/liquid-dsp,cjcliffe/liquid-dsp,cjcliffe/liquid-dsp,JayKickliter/liquid-dsp,jgaeddert/liquid-dsp,cjcliffe/liquid-dsp,biotrump/liquid-dsp,cjcliffe/liquid-dsp,jgaeddert/liquid-dsp,JayKickliter/liquid-dsp,andrepuschmann/liquid-dsp,manuts/liquid-dsp,wangning223/liquid-dsp,JayKickliter/liquid-dsp,andrepuschmann/liquid-dsp,andrepuschmann/liquid-dsp,JayKickliter/liquid-dsp,andrepuschmann/liquid-dsp,andrepuschmann/liquid-dsp,manuts/liquid-dsp