iio: sca3000: switch IRQ handling to devm helpers

iio: sca3000: switch IRQ handling to devm helpers

Convert the threaded IRQ registration to devm_request_threaded_irq() so
that the probe and remove paths can drop manual freeing of irqs.

No functionality change.

Suggested-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>