Compilation success with pthreads enabled

- The project can be compiled with pthread enabled on opencv build
	- FIXME: Needed to add a call to pthread_cond_init() in the main component for the linker to work.
	The pthread_cond implementation is done in esp-idf/components/pthreads/
- The optimization hasn't yet enhanced the benchmark performances, hasn't found why for now

modules/core/src/parallel.cpp

@@ -950,6 +950,10 @@ int cv::getNumberOfCPUs(void)
 
 #endif
 
+#if defined(ESP32)
+    ncpus = 2;      // TODO: Only for ESP32D0WD
+#endif
+
     return ncpus != 0 ? ncpus : 1;
 }