ath11k: clean up BDF download functions

In current code, AHB/PCI uses two separate functions to download
BDF file. Refactor code and make a common function to send QMI BDF
download request for both AHB and PCI devices. This patch has no
functional change.

Tested-on: IPQ8074 hw2.0 AHB WLAN.HK.2.4.0.1-00009-QCAHKSWPL_SILICONZ-1
Tested-on: QCN9074 hw1.0 PCI WLAN.HK.2.4.0.1-01838-QCAHKSWPL_SILICONZ-1

Signed-off-by: Anilkumar Kolli <akolli@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210721201927.100369-3-jouni@codeaurora.org