input: remove s3c24xx touchscreen driver

The s3c24xx SoC support and its adc driver was removed, so this driver
has no remaining users.

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>