Bluetooth: btusb: support download nvm with different board id for wcn6855

we define many nvm files for wcn6855 btsoc and host driver
should find the correct nvm file based on board ID and then
download it.

Signed-off-by: Tim Jiang <tjiang@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>