Bluetooth: mt7921s: Add .btmtk_get_codec_config_data

add .btmtk_get_codec_config_data to get codec configuration data.

In HFP offload usecase, controllers need to be set codec details before
opening SCO. This callback function is used to fetch vendor specific codec
config data.

This is a preliminary patch to add the WBS support to the MT7921 driver.

Reviewed-by: Mark Chen <markyawenchen@gmail.com>
Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Yake Yang <yake.yang@mediatek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>