ALSA: hda: Use STAC_DELL_M6_BOTH quirk for Dell Studio XPS 1645

BugLink: https://launchpad.net/bugs/553002

The OR has verified that the dell-m6 model quirk is necessary for audio
to be audible by default on the Dell Studio XPS 1645.

This change is necessary for 2.6.32.11 and 2.6.33.2 alike.

Reported-by: Robert Chambers
Tested-by: Robert Chambers
Cc: <stable@kernel.org>
Signed-off-by: NDaniel T Chen <crimsun@ubuntu.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_sigmatel.c

@@ -1607,6 +1607,8 @@ static struct snd_pci_quirk stac92hd73xx_cfg_tbl[] = {
 				"Dell Studio 1555", STAC_DELL_M6_DMIC),
 	SND_PCI_QUIRK(PCI_VENDOR_ID_DELL, 0x02bd,
 				"Dell Studio 1557", STAC_DELL_M6_DMIC),
+	SND_PCI_QUIRK(PCI_VENDOR_ID_DELL, 0x02fe,
+				"Dell Studio XPS 1645", STAC_DELL_M6_BOTH),
 	{} /* terminator */
 };