iio: admv1013: replace redundant ternary operator with just len

iio: admv1013: replace redundant ternary operator with just len

The variable ret is being assigned a return value and non-zero error
return paths are taken at all stages. At the end of the function ret
is always zero, so the ternary operator checking for zero ret is
redundant and can be replaced with just len instead.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250507134502.254736-1-colin.i.king@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>