DynamicTablesPkg: Clear pointer in node creation fcts

The following functions:
- AmlCreateRootNode()
- AmlCreateObjectNode()
- AmlCreateDataNode()
create a node and return it by populating a pointer. This pointer
should only be considered/used if the function returns successfully.
Otherwise, the value stored in this pointer should be ignored.

For their error handling, some other functions assume that this
pointer is reset to NULL if an error occurs during a node creation.
To make this assumption correct, explicitly clear this input pointer.

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>

DynamicTablesPkg/Library/Common/AmlLib/CodeGen/AmlResourceDataCodeGen.c

@@ -33,7 +33,9 @@
                             RdNode is then added at the end of the variable
                             list of resource data elements, but before the
                             "End Tag" Resource Data.
-  @param [out] NewRdNode    If not NULL, update the its value to RdNode.
+  @param [out] NewRdNode    If not NULL:
+                             - and Success, contains RdNode.
+                             - and Error, reset to NULL.
 
   @retval  EFI_SUCCESS            The function completed successfully.
   @retval  EFI_INVALID_PARAMETER  Invalid parameter.
@@ -52,7 +54,7 @@ LinkRdNode (
   AML_OBJECT_NODE   *BufferOpNode;
 
   if (NewRdNode != NULL) {
-    *NewRdNode = RdNode;
+    *NewRdNode = NULL;
   }
 
   if (ParentNode != NULL) {
@@ -85,6 +87,10 @@ LinkRdNode (
     }
   }
 
+  if (NewRdNode != NULL) {
+    *NewRdNode = RdNode;
+  }
+
   return Status;
 
 error_handler: