hw/audio: Simplify hda audio init

No return values are used anywhere, so switch the functions to be void
and add support for error reporting using errp for use in next patches.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <cd1df4ad2a6fae969c4a02a77955c4a8c0d430b6.1650874791.git.mkletzan@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>