lowlevel-blt-bench: move usage to a function

Move printing of usage into a new function and use argv[0] as the
program name. This will help printing usage from multiple places.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Ben Avison <bavison@riscosopen.org>
1 file changed