of/resolver: Switch to new local fixups format.

The original resolver format is way too cryptic, switch
to using a tree based format that gets rid of repetitions,
is more compact and readable.

At the same time, update the selftests to using the new local fixups
format.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[grant.likely: Squashed in testcase changes and merged similar functions]
Signed-off-by: Grant Likely <grant.likely@linaro.org>