driconf: fix force_gl_vendor description
The option is not a toggle to "allow GPU vendor to be overridden", it *is* the override. Fixes: dca119f1 ("mesa/gallium: add dric option to allow overriding GL vendor string") Signed-off-by:Eric Engestrom <eric@engestrom.ch> Reviewed-by:
Marek Olšák <marek.olsak@amd.com> Part-of: <mesa/mesa!6207>