platform/chrome: fix kernel-doc warning for last_resume_result

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 'last_resume_result' not described in 'cros_ec_device'

Cc: Evan Green <evgreen@chromium.org>
Fixes: 8c3166e1 ("mfd / platform: cros_ec_debugfs: Expose resume result via debugfs")
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20230111055728.708990-4-tzungbi@kernel.org