lavu/tests/cpu: stop processing the thread count

Just print it as it is.

Needed by the following commit.

libavutil/tests/cpu.c

@@ -106,7 +106,7 @@ int main(int argc, char **argv)
     int cpu_flags_raw = av_get_cpu_flags();
     int cpu_flags_eff;
     int cpu_count = av_cpu_count();
-    char threads[5] = "auto";
+    const char *threads = "auto";
     int i;
 
     for(i = 0; cpu_flag_tab[i].flag; i++) {
@@ -136,11 +136,7 @@ int main(int argc, char **argv)
         }
         case 't':
         {
-            int len = av_strlcpy(threads, optarg, sizeof(threads));
-            if (len >= sizeof(threads)) {
-                fprintf(stderr, "Invalid thread count '%s'\n", optarg);
-                return 2;
-            }
+            threads = optarg;
         }
         }
     }