wcn36xx: Reduce spinlock in indication handler

The purpose of pushing indication on a list and handle these in a
separate worker is to allow the handlers to sleep. It does therefor not
make much sense to hold the queue spinlock through the entire indication
worker function.

By removing items from the queue early we don't need to hold the lock
throughout the indication worker, allowing the individual handlers to
sleep.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>