synthio: Fix sweep-type pitch bends

The accumulator saturate logic was wrong, and the sweep was never restarted
either

Author: jepler

shared-module/synthio/Note.c

@@ -193,6 +193,9 @@ void synthio_note_recalculate(synthio_note_obj_t *self, int32_t sample_rate) {
 
 void synthio_note_start(synthio_note_obj_t *self, int32_t sample_rate) {
     synthio_note_recalculate(self, sample_rate);
+    if (self->bend_mode != SYNTHIO_BEND_MODE_VIBRATO) {
+        self->bend_state.phase = 0;
+    }
 }
 
 uint32_t synthio_note_envelope(synthio_note_obj_t *self) {

shared-module/synthio/__init__.c

@@ -554,8 +554,9 @@ STATIC int synthio_lfo_step_common(synthio_lfo_state_t *state, uint16_t dur) {
     return whole_phase;
 }
 STATIC int synthio_lfo_sweep_common(synthio_lfo_state_t *state, uint16_t dur) {
+    uint32_t old_phase = state->phase;
     uint16_t whole_phase = synthio_lfo_step_common(state, dur);
-    if (state->phase < state->dds) {
+    if (state->phase < old_phase) {
         state->phase = 0xffffffff;
     }
     return whole_phase;