Update comments for vendor-specific parameters API.

     * ones stated in VendorKeyValue documentation (a requirement of key

     * prefixes).

     *

     * Results vector may not contain a result for each parameter being set,

     * it can even be empty.

     * For each pair in the result vector, the key must be one of the keys

     * contained in the input (possibly with wildcards expanded), and the value

     * must be a vendor-specific result status (i.e. the string "OK" or an error

     * code). The implementation may choose to return an empty vector, or only

     * return a status for a subset of the provided inputs, at its discretion.

     *

     * Application and HAL must not use keys with unknown prefix. In particular,

     * it must not place a key-value pair in results vector for unknown key from

     *

     * @param parameters Vendor-specific key-value pairs.

     * @return results Operation completion status for parameters being set.

     *                 Value format for result status is vendor-specific.

     */

    setParameters(vec<VendorKeyValue> parameters)

            generates (vec<VendorKeyValue> results);