Some configuration dialogs display wrong units for frequency settings

In https://github.com/mudlord/fb2k/blob/master/foobar2000/foo_dsp_effect/foo_dsp_effect.rc I suggest you make these fixes so the dialogs have the correct units for frequency settings:

line 309: replace % with Hz
line 390: replace db with Hz

For consistency and correctness, maybe also do a search & replace for hz→Hz and db→dB.
