staging:iio: iio_trigger contains defunct owner field. Remove it.

This field moved into the trigger_ops structure a while back, but somehow
never quite got cleared up.  This clears the last few drivers to set it
(nothing uses it) and gets rid of it entirely.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>