dtc: Run relevant checks on dtb input as well as dts

This patch adjusts the testsuite to run most of the tests for the tree
checking code on input in dtb form as well as dts form.  Some checks
which only make sense for dts input (like reference handling) are
excluded, as are those which currently take dtb input because they
rely on things which cannot be lexically constructed in a dts file.

This shows up two small bugs in dtc, which are also corrected.

First, the name_properties test which was is supposed to remove
correctly formed 'name' properties (because they can be reconstructed
from tne node name) was instead removing 'name' properties even if
they weren't correct.

Secondly, when using dtb or fs input, the runtime tree in dtc did not
have the parent pointer initialized propertly because.built
internally.  The appropriate initialization is added to the
add_child() function.

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