wil6210: fix PCIe bus mastering in case of interface down

In case of interface down, radio is turned off but PCIe mastering is
not cleared.
This can cause unexpected PCIe access to the shutdown device.
Fix this by clearing PCIe mastering also in case interface is down

Signed-off-by: Lazar Alexei <qca_ailizaro@qca.qualcomm.com>
Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>