test: Support tests which can only be run manually

At present we normally write tests either in Python or in C. But most
Python tests end up doing a lot of checks which would be better done in C.
Checks done in C are orders of magnitude faster and it is possible to get
full access to U-Boot's internal workings, rather than just relying on
the command line.

The model is to have a Python test set up some things and then use C code
(in a unit test) to check that they were done correctly. But we don't want
those checks to happen as part of normal test running, since each C unit
tests is dependent on the associate Python tests, so cannot run without
it.

To acheive this, add a new UT_TESTF_MANUAL flag to use with the C 'check'
tests, so that they can be skipped by default when the 'ut' command is
used. Require that tests have a name ending with '_norun', so that pytest
knows to skip them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/test-dm.c b/test/dm/test-dm.c
index eb35813..66cc2bc 100644
--- a/test/dm/test-dm.c
+++ b/test/dm/test-dm.c
@@ -36,7 +36,7 @@
 	int ret;
 
 	ret = ut_run_list("driver model", "dm_test_", tests, n_ents, test_name,
-			  runs_per_text);
+			  runs_per_text, false);
 
 	return ret ? CMD_RET_FAILURE : 0;
 }