wcn36xx: dequeue all pending indicator messages

In case wcn36xx_smd_rsp_process() is called more than once before
hal_ind_work was dispatched, the messages will end up in hal_ind_queue,
but wcn36xx_ind_smd_work() will only look at the first message in that
list.

Fix this by dequeing the messages from the list in a loop, and only stop
when it's empty.

This issue was found during a review of the driver. In my tests, that
race never actually occured.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>