Bluetooth: btqca: Add WCN6855 firmware priority selection feature

Bluetooth: btqca: Add WCN6855 firmware priority selection feature

Historically, WCN685x and QCA2066 shared the same firmware files.
Now, changes are planned for the firmware that will make it incompatible
with QCA2066, so a new firmware name is required for WCN685x.

Test Steps:
 - Boot device
 - Check the BTFW loading status via dmesg

Sanity pass and Test Log:
QCA Downloading qca/wcnhpbftfw21.tlv
Direct firmware load for qca/wcnhpbftfw21.tlv failed with error -2
QCA Downloading qca/hpbftfw21.tlv

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Shuai Zhang <shuai.zhang@oss.qualcomm.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>