linker: undefine the no-ops dt macros at the end of the file

Undefine the DT_NODE_HAS_STATUS and DT_NODE_HAS_STATUS_OKAY no nop at
the end of the file so other uses can include devicetree.h without
generating a compiler warning.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>