The logic under graph_add_file should create, for every entry, a
__name name array for all entries of the tree. If this fails, the
symlink parsing will break.

Add an error if this ever happens.

While here, improve the output of data dumper to be more
compact and to avoid displaying things like $VAR1=.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/e7dd4d70e206723455d50c851802c8bb6c34941d.1632750315.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>