[ALSA] Fix 'semaphore is not ready' problem with snd-intel8x0m

Intel8x0-modem driver
With some intel based ac97 modems codec access semaphore is not cleared
after 0x54 AC97 register (GPIO_STATUS) reads. This may causes problems
with newly applied modem mixer (Off-hook switch) and in other cases.
Signed-off-by: NSasha Khapyorsky <sashak@smlink.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/intel8x0m.c

@@ -500,6 +500,8 @@ static unsigned short snd_intel8x0_codec_read(ac97_t *ac97,
 			res = 0xffff;
 		}
 	}
+	if (reg == AC97_GPIO_STATUS)
+		iagetword(chip, 0); /* clear semaphore */
 	return res;
 }