platform/chrome: cros_ec_proto: use cros_ec_map_error()

Use cros_ec_map_error() in cros_ec_get_host_event_wake_mask().

The behavior of cros_ec_get_host_event_wake_mask() slightly changed.  It
is acceptable because the caller only needs it returns negative integers
for indicating errors.  Especially, the EC_RES_INVALID_COMMAND still
maps to -EOPNOTSUPP.

Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-7-tzungbi@kernel.org