As promised, this is my change:
linux/sound/mips/au1x00.c, function "snd_au1000_ac97_new":
...
/* Initialise Au1000's AC'97 Control Block */
au1000->ac97_ioport->cntrl = AC97C_RS | AC97C_CE;
udelay(10);
au1000->ac97_ioport->cntrl = AC97C_CE;
/* Original delay 10us */
/* udelay(10); */
/* New delay 200ms */
mdelay(200);
/* Initialise External CODEC -- cold reset */
au1000->ac97_ioport->config = AC97C_RESET;
udelay(10);
au1000->ac97_ioport->config = 0x0;
mdelay(5);
...