apps/speed.c: Fix eddsa sign and verify output with -multi option

Fixes #10261
CLA: trivial

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10285)

(cherry picked from commit 1ac7e153)