dtbuilder: fixup TOG copyrights issue in generated files.

dtbuilder: fixup TOG copyrights issue in generated files.

The TOG copyrights were being removed after a rebuild, leaving behind
the scary "RESTRICTED" copyright text that was originally there.

The issue was that the TOG copyrights were not properly embedded
within a 'DTB_USER_CODE_START' code block.

dtcodegen does not preserve any code outside DT_USER_CODE START and
END blocks.

Additionally, these objects are built with -merge by dtcodgen, so the
existing 'RESTRICTED' header within the codeblocks was being retained.