wil6210: treat "unhandled event" as warning instead of error

FW is allowed to generate WMI events that are not handled by this driver.
Treat such case as warning instead of error.

Signed-off-by: Dedy Lansky <qca_dlansky@qca.qualcomm.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>