iio: adc: ina2xx: Remove bogus cast for data argument

iio_push_to_buffers_with_timestamp expects a void pointer, so the cast
is both unnecessary and misleading.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>