bootloader_support: Add C++ header guards

As reported on forum https://esp32.com/viewtopic.php?f=13&t=11173&p=45470

components/bootloader_support/include/bootloader_util.h

@@ -16,6 +16,10 @@
 
 #include <stddef.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @brief Check if half-open intervals overlap
  *
@@ -33,3 +37,7 @@ static inline bool bootloader_util_regions_overlap(
     assert(end2>start2);
     return (end1 > start2 && end2 > start1);
 }
+
+#ifdef __cplusplus
+}
+#endif