staging:iio:addac:adt7316 replace abuse of buffer events.

Currently squashed the fault condition from external
temperature sensor - lots of other issues to be fixed
with this driver which obeys almost no elements of the
abi.

V2: removed a couple of usused variables that sparse found.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>