iio: chemical: atlas-sensor: use iio_trigger_poll_nested() to fix remove UAF

Summary

In the Linux kernel, the following vulnerability has been resolved: iio: chemical: atlas-sensor: use iio_trigger_poll_nested() to fix remove UAF The atlas driver requests its hardware data-ready IRQ with devm_request_threaded_irq(); its threaded handler queues an irq_work, atlas_work_handler(), that calls iio_trigger_poll(data->trig). The IRQ is devm-managed, so free_irq() runs from the devres unwind after atlas_remove() returns without flushing that irq_work. Once a buffer is enabled, conversion-complete IRQs keep firing and queueing it; a pending irq_work can therefore run after the unwind has freed atlas_data/indio_dev and the trigger, when atlas_work_handler() derives the atlas_data pointer via container_of() and dereferences data->trig, a use-after-free. Call iio_trigger_poll_nested() directly from the threaded handler instead of bouncing through irq_work. free_irq() then drains the threaded handler, closing the window; other iio drivers with a threaded data-ready IRQ do the same (e.g. bmi270). This issue was found by an in-house static analysis tool.