iio: adc: exynos_adc: Drop platform data support

There are no Samsung Exynos SoC ADC driver users which bind via platform
ID, thus platform data is never set and can be dropped.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250830-s3c-cleanup-adc-v2-3-4f8299343d32@linaro.org


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