test: blkmap: Add test suite

Verify that:

- Block maps can be created and destroyed
- Mappings aren't allowed to overlap
- Multiple mappings can be attached and be read/written from/to

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index e0a1f8c..ec8b149 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -799,6 +799,7 @@
 F:	cmd/blkmap.c
 F:	drivers/block/blkmap.c
 F:	include/blkmap.h
+F:	test/dm/blkmap.c
 
 BOOTDEVICE
 M:	Simon Glass <sjg@chromium.org>