log: test: Add a pytest for logging

Add a test which tries out various filters and options to make sure that
logging works as expected.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 9d8a82e..e1227f8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -317,6 +317,7 @@
 F:	common/log.c
 F:	cmd/log.c
 F:	test/log/log_test.c
+F:	test/py/tests/test_log.py
 
 MICROBLAZE
 M:	Michal Simek <monstr@monstr.eu>