CVE-2026-98657: iio: proximity: pulsedlight: fix iio_device left registered on PM setup failure

In the Linux kernel, the following vulnerability has been resolved: iio: proximity: pulsedlight: fix iio_device left registered on PM setup failure pm_runtime_set_active() failing in probe() jumps to error_unreg_buffer, which only calls iio_triggered_buffer_cleanup() -- it does not undo the iio_device_register() that already succeeded a few lines above. probe() then returns the error, the devm-managed indio_dev is freed, but the iio core still has it registered: the sysfs/chardev nodes stay live and point at freed memory. Add an error_unreg_dev label that unregisters the iio device before falling through to the existing buffer cleanup, mirroring the teardown order already used in lidar_remove().