Fix copy&paste error found in Coverity scan

Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7377)

apps/speed.c

@@ -2947,7 +2947,7 @@ int speed_main(int argc, char **argv)
 
             if (rsa_count <= 1) {
                 /* if longer than 10s, don't do any more */
-                for (testnum++; testnum < EC_NUM; testnum++)
+                for (testnum++; testnum < ECDSA_NUM; testnum++)
                     ecdsa_doit[testnum] = 0;
             }
         }