selftests: move vDSO tests from Documentation/vDSO

Remove vDSO from Makefile to move the to selftests. Update vDSO Makefile
to work under selftests. vDSO will not be run as part of selftests suite
and will not be included in install targets. They can be built separately
for now.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
diff --git a/Documentation/Makefile b/Documentation/Makefile
index 8cd6d1a..085b917 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -1,3 +1,3 @@
 subdir-y := accounting auxdisplay blackfin \
 	ia64 laptops mic misc-devices \
-	networking pcmcia timers vDSO watchdog
+	networking pcmcia timers watchdog