Remove redundant fdtdump test code

The overall test runner script, for the fdtdump tests invokes the helper
script fdtdump-runtest.sh.  It then includes directly some code very
similar to fdtdump-runtest.sh, which is never reached due to a "return".

Remove the never-reached test code.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>