wil6210: fix for HW bug in interrupt setup logic

Hardware bug triggered by the MSI init while INTx asserted for some reason.
De-assert INTx prior to MSI set-up

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>