Fixes the following W=1 kernel build warning(s):

 drivers/input/keyboard/cros_ec_keyb.c:72: warning: cannot understand function prototype: 'struct cros_ec_bs_map '
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Benson Leung <bleung@chromium.org>
Link: https://lore.kernel.org/r/20201104162427.2984742-8-lee.jones@linaro.org
[dtor: fixed up docbook comments for cros_ec_keyb structure as well]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>