wil6210: fix locking in wmi_call

Switch from spin_lock to spin_lock_irqsave, because
wmi_ev_lock is used inside interrupt handler.

Signed-off-by: Lior David <liord@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>