Wince AC97 reset sequence is as follows :
 - GPIO89 is setup as output GPIO, alt.func 1 (AC97_SYSCLK)
 - GPIO28 and GPIO29 are setup as input, alt.func 1 (AC97_BITCLK and AC97_SDATA_IN_0)
 - GPIO30 and GPIO31 are set (GPSR..)
 - GPIO30 and GPIO31 are setup as output, alt.func 2 (AC97_SDATA_OUT, AC97_SYNC)
 - GPIO95 is set
 - ICMR: AC97 irq is masqued
 - CKEN |= CKEN2
 - call ColdReset()
 - call WarmReset()
 - write 0x1111 into ac97 register 0
 - call mdelay(10)
 - call ColdReset()
 - call WarmReset()


ColdReset()
 - GCR = 0
 - GCR |= 1 (AC97 interrupt generator)
 - GEDR2: Clear edge detect status on GPIO95
 - GPIO87 is setup as normal gpio
 - GPIO95 is set
 - mdelay(10)
 - GPIO95 is cleared
 - mdelay(10)
 - GPIO95 is set
 - GCR |= 2 (nRST = 1 => end of cold reset)
 - mdelay(100)
 - for (i=0; i < 1000; i++)
     test GSR.PCRDY == 1
     udelay(1/3.25)
 - return success if (GSR.PCRDY == 1)

WarmReset()
 - GCR |= 0xc0004 (SRDY_IE | PRDY_IE | WRST)
 - udelay(5/3.25)
 - for (i=0; i < 1000; i++)
     test GSR.PCRDY == 1
     udelay(1/3.25)
 - return success if (GSR.PCRDY == 1)