airo: use set_current_state macro

Use set_current_state macro instead of current->state = TASK_RUNNING.

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200702015701.8606-1-vulab@iscas.ac.cn