dm: core: Update comments for default-FDT ofnode functions

Some ofnode functions can only operate on the default device tree, i.e.
U-Boot's control FDT. Add comments to that effect. Fix up the reference to
device tree bindings while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/ofnode.h b/include/dm/ofnode.h
index 3a514f7..0c5a883 100644
--- a/include/dm/ofnode.h
+++ b/include/dm/ofnode.h
@@ -908,6 +908,8 @@
  * This looks for a property within the /chosen node and returns its value,
  * checking that it is a valid nul-terminated string
  *
+ * This only works with the control FDT.
+ *
  * @propname: Property name to look for
  * Return: string value if found, else NULL
  */
@@ -919,6 +921,8 @@
  * This looks up a named property in the chosen node and uses that as a path to
  * look up a code.
  *
+ * This only works with the control FDT.
+ *
  * @propname: Property name to look for
  * Return: the referenced node if present, else ofnode_null()
  */
@@ -929,6 +933,8 @@
  *
  * This looks for a property within the /aliases node and returns its value
  *
+ * This only works with the control FDT.
+ *
  * @propname: Property name to look for
  * @sizep: Returns size of property, or `FDT_ERR_...` error code if function
  *	returns NULL
@@ -942,6 +948,8 @@
  * This looks up a named property in the aliases node and uses that as a path to
  * look up a code.
  *
+ * This only works with the control FDT.
+ *
  * @propname: Property name to look for
  * Return: the referenced node if present, else ofnode_null()
  */
@@ -1427,7 +1435,9 @@
  *
  * This reads a property from the /config node of the devicetree.
  *
- * See doc/config.txt for bindings
+ * This only works with the control FDT.
+ *
+ * See doc/device-tree-bindings/config.txt for bindings
  *
  * @prop_name:	property name to look up
  * Return: true, if it exists, false if not
@@ -1439,7 +1449,7 @@
  *
  * This reads a property from the /config node of the devicetree.
  *
- * See doc/config.txt for bindings
+ * See doc/device-tree-bindings/config.txt for bindings
  *
  * @prop_name: property name to look up
  * @default_val: default value to return if the property is not found
@@ -1452,7 +1462,9 @@
  *
  * This reads a property from the /config node of the devicetree.
  *
- * See doc/config.txt for bindings
+ * This only works with the control FDT.
+ *
+ * See doc/device-tree-bindings/config.txt for bindings
  *
  * @prop_name: property name to look up
  * Return: string value, if found, or NULL if not