ALSA: hda/sigmatel - Allow auto-switching for dock line-in of HP laptops

Many HP laptops with STAC codecs have a docking station port and BIOS
sets the pins for the input on the dock as a line in.  Because the
generic parser doesn't handle a line in pin as auto-switchable, this
resulted in the manual capture source selection on these laptops.

However, from the usability POV, the automatic switching is easier.
This patch adds the line_in_auto_switch hint in the fixup function for
these laptops.  Even if no dock port is present, this should be
harmless as the generic parser allows the auto-switching only in a
limited situation (all three pins are located in different
positions).
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_sigmatel.c

@@ -2089,6 +2089,9 @@ static void stac92hd83xxx_fixup_hp(struct hda_codec *codec,
 		codec_dbg(codec, "mute LED gpio %d polarity %d\n",
 				spec->gpio_led,
 				spec->gpio_led_polarity);
+
+	/* allow auto-switching of dock line-in */
+	spec->gen.line_in_auto_switch = true;
 }
 
 static void stac92hd83xxx_fixup_hp_zephyr(struct hda_codec *codec,