Bluetooth: qca: fix info leak when fetching board id

Add the missing sanity check when fetching the board id to avoid leaking
slab data when later requesting the firmware.

Fixes: a7f8dedb ("Bluetooth: qca: add support for QCA2066")
Cc: stable@vger.kernel.org	# 6.7
Cc: Tim Jiang <quic_tjiang@quicinc.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>