test:dm:fix typo

Fix typos in the 'test/dm' directory.

Signed-off-by: Yuepeng Xing <xingyuepeng@eswincomputing.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/dm/test-fdt.c b/test/dm/test-fdt.c
index 8bb868b..7cd2d04 100644
--- a/test/dm/test-fdt.c
+++ b/test/dm/test-fdt.c
@@ -592,7 +592,7 @@
 	ut_asserteq_str("dev@2,200", dev->name);
 	ut_asserteq(0xA000, dev_read_addr(dev));
 
-	/* No translation for busses with #size-cells == 0 */
+	/* No translation for buses with #size-cells == 0 */
 	ut_assertok(uclass_find_device_by_seq(UCLASS_TEST_DUMMY, 3, &dev));
 	ut_asserteq_str("dev@42", dev->name);
 	ut_asserteq(0x42, dev_read_addr(dev));