sunxi audio

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

There is a bug port-arm/57031 on sunxi audio device drivers stopping
attaching after the last device tree update.

<https://mail-index.netbsd.org/netbsd-bugs/2022/09/27/msg076184.html>

This is caused by a test in the get_tag functions in each of the
audio drivers, 

An example:

static audio_dai_tag_t
sunxi_i2s_dai_get_tag(device_t dev, const void *data, size_t len)
{
        struct sunxi_i2s_softc * const sc = device_private(dev);

        if (len != 4)
                return NULL;
   
        return &sc->sc_dai;
}

The value of len is calculated from the device tree by the
fdtbus_dai_acquire_index() function. The device tree update changed
this value.

Can anyone remember why the test is needed?