iio: adc: ad7124: Use devm_ managed calls for all of probe() + drop remove()

As not many steps were not already devm_ managed, use
devm_add_action_or_reset() to handle the rest.

This also uses the new devm_ad_sd_setup_buffer_and_trigger() function.

Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Alexandru Ardelean <aardelean@deviqon.com>
Link: https://lore.kernel.org/r/20210513120752.90074-12-aardelean@deviqon.com