drm/amdgpu: drop hw access in non-DC audio fini

We already disable the audio pins in hw_fini so
there is no need to do it again in sw_fini.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4481


Cc: oushixiong <oushixiong1025@163.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>