ALSA: usb-audio: scarlett2: Fix 6i6 Gen 2 line out descriptions

There are two headphone outputs, and they map to the four analogue
outputs.
Signed-off-by: NGeoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/205e5e5348f08ded0cc4da5446f604d4b91db5bf.1624294591.git.g@b4.vuSigned-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/mixer_scarlett_gen2.c

@@ -263,10 +263,10 @@ static const struct scarlett2_device_info s6i6_gen2_info = {
 	.pad_input_count = 2,
 
 	.line_out_descrs = {
-		"Monitor L",
-		"Monitor R",
-		"Headphones L",
-		"Headphones R",
+		"Headphones 1 L",
+		"Headphones 1 R",
+		"Headphones 2 L",
+		"Headphones 2 R",
 	},
 
 	.ports = {