platform/chrome: cros_ec_proto: Make data pointers void

Convert the input and output data pointers for cros_ec_command() to
void pointers so that the callers don't have to cast their custom
structs to uint8_t *.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20210930022403.3358070-4-pmalani@chromium.org