Fix unitialized variables (#609)

Compiling with gcc 13 and -O3 -flto -Werror=uninitialized found two
possibly unitialized variables.

See also: https://bugs.gentoo.org/916722

src/modules/cpuusage/cpuusage.c

@@ -180,6 +180,7 @@ void ffInitCPUUsageOptions(FFCPUUsageOptions* options)
         ffGenerateCPUUsageJsonConfig
     );
     ffOptionInitModuleArg(&options->moduleArgs);
+    options->separate = false;
 }
 
 void ffDestroyCPUUsageOptions(FFCPUUsageOptions* options)