dm: test: Disable some tests that should not run in SPL

Tests are easier to run in U-Boot proper. Running them in SPL does not add
test coverage in most cases. Also some tests use features that are not
available in SPL.

Update the build rules to disable these tests in SPL. We still need
test-main to be able to actually run SPL tests.

Signed-off-by: Simon Glass <sjg@chromium.org>