hwmon: (ads7828) fix Wvoid-pointer-to-enum-cast warning

'chip' is an enum, thus cast of pointer on 64-bit compile test with W=1
causes:

  ads7828.c:142:10: error: cast to smaller integer type 'enum ads7828_chips' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230810093157.94244-3-krzysztof.kozlowski@linaro.org


Signed-off-by: Guenter Roeck <linux@roeck-us.net>