dt-bindings: iio: adc: samsung,exynos: Drop touchscreen support

dt-bindings: iio: adc: samsung,exynos: Drop touchscreen support

With last user of touchscreen via ADC (S3C24xx SoC) gone, drop the
unused has-touchscreen property and optional touchscreen interrupt for
samsung,s3c6410-adc.  The samsung,s5pv210-adc is the only platform
having two interrupts, so add a constrain for that.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/20250830-s3c-cleanup-adc-v2-5-4f8299343d32@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>