of: properties of reserved-memory nodes

The reusable and the no-map property are mutually exclusive.
Clarify this in the documentation.

Acked-by: Grant Likely <[e-mail]>
Signed-off-by: Heinrich Schuchardt <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

···
       system can use that region to store volatile or cached data that
       can be otherwise regenerated or migrated elsewhere.
 
+A node must not carry both the no-map and the reusable property as these are
+logically contradictory.
+
 Linux implementation note:
 - If a "linux,cma-default" property is present, then Linux will use the
   region for the default pool of the contiguous memory allocator.