staging:iio:adis_lib: Use triggered buffer setup helper function

Use the triggered buffer helper functions to setup and tear down the buffer for
the adis library instead of doing this manually. This also means that we switch
away from the deprecated sw_ring buffer and use the kfifo buffer now instead.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>