tests: Clarify dtc overlay tests

This changes the names of the testfiles for a number of the testcases of
the dtc overlay generation functionality to make them shorter and a bit
cleaerer what's going on.  In addition we move some of the check_path
sanity checks closer to the dtc commands they verify.

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