iio: adc: exynos: drop unneeded variable assignment

The initialization of 'ret' variable in probe function is shortly after
overwritten.  This initialization is simply not used.

Addresses-Coverity: Unused value
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20210410164728.8096-1-krzysztof.kozlowski@canonical.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>