iio: cros_ec: Fix the allocation size for cros_ec_command

iio: cros_ec: Fix the allocation size for cros_ec_command

The struct cros_ec_command contains several integer fields and a
trailing array. An allocation size neglecting the integer fields can
lead to buffer overrun.

Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Yiyuan Guo <yguoaz@gmail.com>
Fixes: 974e6f02e27e ("iio: cros_ec_sensors_core: Add common functions for the ChromeOS EC Sensor Hub.")
Link: https://lore.kernel.org/r/20230630143719.1513906-1-yguoaz@gmail.com
Cc: <Stable@vger.kerenl.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>