kmemtrace: Fix typos in documentation.

Corrected the ABI description and the kmemtrace usage guide. Thanks to
Randy Dunlap for noticing these errors.

Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
diff --git a/Documentation/ABI/testing/debugfs-kmemtrace b/Documentation/ABI/testing/debugfs-kmemtrace
index a5ff9a6..5e6a92a 100644
--- a/Documentation/ABI/testing/debugfs-kmemtrace
+++ b/Documentation/ABI/testing/debugfs-kmemtrace
@@ -63,7 +63,7 @@
 data:
 	Feature size	(2 byte)
 	Feature ID	(1 byte)
-	Feature data	(Feature size - 4 bytes)
+	Feature data	(Feature size - 3 bytes)
 
 
 Users: