Bluetooth: mt7921s: Enable SCO over I2S

The driver has to issue the specific command to enable Bluetooth SCO over
the I2S/PCM interface on mt7921s, that is supported since the firmware
with version 20211222191101 was added, and the patch would not cause any
harm even when the old firmware is applied.

The SCO profile with the patch was tested by setting up a VOIP application,
connected to HFP device, checked telephony function can work normally.

Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Mark Chen <mark-yw.chen@mediatek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>