Documentation: use subdir-y to avoid unnecessary built-in.o files

Change the Documentation makefiles from obj-m to subdir-y
to avoid generating unnecessary built-in.o files since nothing
in Documentation/ is ever linked in to vmlinux.

Signed-off-by: Peter Foley <pefoley2@pefoley.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/misc-devices/Makefile b/Documentation/misc-devices/Makefile
new file mode 100644
index 0000000..e2b7aa4
--- /dev/null
+++ b/Documentation/misc-devices/Makefile
@@ -0,0 +1 @@
+subdir-y := mei