dtoc: Support widening a bool value

At present if we see 'ranges' property (with no value) we assume it is a
boolean, as per the devicetree spec.

But another node may define 'ranges' with a value, forcing us to widen it
to an int array. At present this is not supported and causes an error.

Fix this and add some test cases.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Tom Rini <trini@konsulko.com>