Fix typo in spiffs config and update submodule

Fixes github issues #1012 and #1013

https://github.com/espressif/esp-idf/issues/1012
https://github.com/espressif/esp-idf/issues/1013

components/spiffs/include/esp_spiffs.h

@@ -18,6 +18,10 @@
 #include <stdbool.h>
 #include "esp_err.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @brief Configuration structure for esp_vfs_spiffs_register
  */
@@ -91,4 +95,8 @@ esp_err_t esp_spiffs_format(const char* partition_label);
  */
 esp_err_t esp_spiffs_info(const char* partition_label, size_t *total_bytes, size_t *used_bytes);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _ESP_SPIFFS_H_ */