log: Add a test command

Add a command which exercises the logging system.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 7cda689..9d8a82e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -316,6 +316,7 @@
 T:	git git://git.denx.de/u-boot.git
 F:	common/log.c
 F:	cmd/log.c
+F:	test/log/log_test.c
 
 MICROBLAZE
 M:	Michal Simek <monstr@monstr.eu>