Warm reboot can not reset controller qca6390 due to
lack of controllable power supply, so causes firmware
download failure during enable.

Fixed by sending VSC EDL_SOC_RESET to reset qca6390
within added device shutdown implementation.
Signed-off-by: Zijun Hu <zijuhu@codeaurora.org>
Tested-by: Zijun Hu <zijuhu@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>