dm: core: Add size operations on device tree references

Add functions to add size of addresses in the device tree using ofnode
references.

If the size is not set, return FDT_SIZE_T_NONE.

Signed-off-by: Chen Guanqiao <chenguanqiao@kuaishou.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/dm/ofnode.h

@@ -510,6 +510,16 @@ phys_addr_t ofnode_get_addr_index(ofnode node, int index);
  */
 phys_addr_t ofnode_get_addr(ofnode node);
 
+/**
+ * ofnode_get_size() - get size from a node
+ *
+ * This reads the register size from a node
+ *
+ * @node: node to read from
+ * @return size of the address, or FDT_SIZE_T_NONE if not present or invalid
+ */
+fdt_size_t ofnode_get_size(ofnode node);
+
 /**
  * ofnode_stringlist_search() - find a string in a string list and return index
  *