core: flash: implement flash_sync() to sync buffered data

include/flash.h

@@ -15,6 +15,7 @@ struct flash_ops {
 	size_t (* copy)(struct flash_dev *dev, uint32_t dst, uint32_t src, size_t len);
 	int (* is_erased)(struct flash_dev *dev, uint32_t addr);
 	int (* erase)(struct flash_dev *dev, uint32_t addr);
+	int (* sync)(struct flash_dev *dev);
 };
 
 struct flash_dev {
@@ -38,3 +39,4 @@ size_t flash_write0(struct flash_dev *dev, uint32_t addr, size_t len);
 size_t flash_copy(struct flash_dev *dev, uint32_t dst, uint32_t src, size_t len);
 int flash_is_erased(struct flash_dev *dev, uint32_t addr, size_t len);
 int flash_erase(struct flash_dev *dev, uint32_t addr, size_t len);
+int flash_sync(struct flash_dev *dev);

source/core/flash.c

@@ -153,3 +153,14 @@ int flash_erase(struct flash_dev *dev, uint32_t addr, size_t len)
 
 	return 0;
 }
+
+int flash_sync(struct flash_dev *dev)
+{
+	if (!dev)
+		return -1;
+
+	if (!dev->ops->sync)
+		return 0;
+
+	return dev->ops->sync(dev);
+}