Bluetooth: btusb: mediatek: reset the controller before downloading the fw

Reset the controller before downloading the firmware to improve its
reliability. This includes situations like cold or warm reboots, ensuring
the controller is in its initial state before starting the firmware
download.

Co-developed-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Co-developed-by: Chris Lu <chris.lu@mediatek.com>
Signed-off-by: Chris Lu <chris.lu@mediatek.com>
Signed-off-by: Hao Qin <hao.qin@mediatek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>