util/format: remove left-over util_format_description_table declaration

Fixes: 3c45c4bc ("util: Cope with the fact that formats in u_format.csv are not ordered.")
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
(cherry picked from commit cc7a64f1)