android: camera_metadata: Add method to update an entry

Add a method to update an existing metadata tag entry, by wrapping
the update_metadata_entry() function provided by the Android
metadata library.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/android/camera_metadata.h

@@ -19,6 +19,7 @@ public:
 
 	bool isValid() const { return valid_; }
 	bool addEntry(uint32_t tag, const void *data, size_t data_count);
+	bool updateEntry(uint32_t tag, const void *data, size_t data_count);
 
 	camera_metadata_t *get();
 	const camera_metadata_t *get() const;