[non-BE] Resolve "Missing HF synth reset for output at 16 kHz"

• Related issues: #2313 (closed)
• Requested reviewers:

Reason why this change is needed

• There is missing a HF synth reset for outputs at 16 kHz.

Description of the change

• Call hf_synth_reset_fx() also for 16 kHz outputs.

Affected operating points

• Not BE for outputs at 16 kHz at bitrates with core switching.