iio: light: as73211: Ensure buffer holes are zeroed

Given that the buffer is copied to a kfifo that ultimately user space
can read, ensure we zero it.

Fixes: 403e5586 ("iio: light: as73211: New driver")
Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20250802164436.515988-2-jic23@kernel.org


Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>