synthio: midi_to_hz: remove arbitrary note number limitation

The underlying routine can return numbers for higher and lower
octaves. Other bits of the code might have frequency limitations
but that doesn't mean we shouldn't let someone get a ~4Hz "note"
by sending in (-12), because that's actually totally plausible as
an LFO frequency.

Author: jepler

shared-bindings/synthio/__init__.c

@@ -276,7 +276,7 @@ MP_DEFINE_CONST_FUN_OBJ_KW(synthio_from_file_obj, 1, synthio_from_file);
 //|
 
 STATIC mp_obj_t midi_to_hz(mp_obj_t arg) {
-    mp_float_t note = mp_arg_validate_obj_float_range(arg, 0, 127, MP_QSTR_note);
+    mp_float_t note = mp_arg_validate_type_float(arg, MP_QSTR_note);
     return mp_obj_new_float(common_hal_synthio_midi_to_hz_float(note));
 }
 MP_DEFINE_CONST_FUN_OBJ_1(synthio_midi_to_hz_obj, midi_to_hz);