iio: cros_ec_sensors: Use devm to setup the triggered buffer.

Use resourced managed function devm_iio_triggered_buffer_setup
to make error path simpler and be able to get rid of the remove
function.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>