Grouped extern C statements

Author: lpbeliveau-silabs

src/platform/silabs/efr32/ThreadStackManagerImpl.cpp

@@ -41,14 +41,11 @@
 
 extern "C" {
 #include "platform-efr32.h"
-}
-
-// Forward declaration
-extern "C" otInstance * otGetInstance(void);
-
+otInstance * otGetInstance(void);
 #if CHIP_DEVICE_CONFIG_THREAD_ENABLE_CLI
-extern "C" void otAppCliInit(otInstance * aInstance);
-#endif
+void otAppCliInit(otInstance * aInstance);
+#endif // CHIP_DEVICE_CONFIG_THREAD_ENABLE_CLI
+}
 
 namespace chip {
 namespace DeviceLayer {