platform/chrome: fix kernel-doc warning for suspend_timeout_ms

Fix the following kernel-doc warning:

$ ./scripts/kernel-doc -none include/linux/platform_data/cros_ec_proto.h
include/linux/platform_data/cros_ec_proto.h:187: warning: Function
parameter or member 'suspend_timeout_ms' not described in 'cros_ec_device'

Cc: Evan Green <evgreen@chromium.org>
Fixes: e8bf17d5 ("platform/chrome: cros_ec: Expose suspend_timeout_ms in debugfs")
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20230111055728.708990-3-tzungbi@kernel.org