iio: adc: ad7266: Fix variable checking bug

commit a2b86132 upstream.

The ret variable was not checked after iio_device_release_direct_mode(),
which could possibly cause errors

Fixes: c70df20e

 ("iio: adc: ad7266: claim direct mode during sensor read")
Signed-off-by: Fernando Yang <hagisf@usp.br>
Link: https://lore.kernel.org/r/20240603180757.8560-1-hagisf@usp.br
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>