Bluetooth: btusb: Add support USB ALT 3 for WBS

Because mSBC frames do not need to be aligned to the SCO packet
boundary. Using USB ALT 3 let HCI payload >= 60 bytes, let mSBC
data satisfy 60 Bytes avoid payload unaligned situation and fixed
some headset no voise issue.

USB Alt 3 supported also need HFP support transparent MTU in 72 Bytes.
Signed-off-by: Hilda Wu <hildawu@realtek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/bluetooth/btusb.c

@@ -1756,6 +1756,13 @@ static void btusb_work(struct work_struct *work)
 			 * which work with WBS at all.
 			 */
 			new_alts = btusb_find_altsetting(data, 6) ? 6 : 1;
+			/* Because mSBC frames do not need to be aligned to the
+			 * SCO packet boundary. If support the Alt 3, use the
+			 * Alt 3 for HCI payload >= 60 Bytes let air packet
+			 * data satisfy 60 bytes.
+			 */
+			if (new_alts == 1 && btusb_find_altsetting(data, 3))
+				new_alts = 3;
 		}
 
 		if (btusb_switch_alt_setting(hdev, new_alts) < 0)