iio: staging: sca3000: hide stufftoread logic

Change sca3000_ring implementation so that it exports a data_available
function to iio.

Signed-off-by: Josselin Costanzi <josselin.costanzi@mobile-devices.fr>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --cc drivers/iio/industrialio-buffer.c
Simple merge

diff --cc drivers/staging/iio/accel/sca3000_ring.c
Simple merge