[update] support fal api for c++ (#5784)

components/fal/inc/fal.h

@@ -15,6 +15,10 @@
 #include <fal_cfg.h>
 #include "fal_def.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * FAL (Flash Abstraction Layer) initialization.
  * It will initialize all flash device and all flash partition.
@@ -149,4 +153,8 @@ struct rt_device *fal_mtd_nor_device_create(const char *parition_name);
  */
 struct rt_device *fal_char_device_create(const char *parition_name);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _FAL_H_ */