dlm: move plock code from gfs2

Move the code that handles cluster posix locks from gfs2 into the dlm
so that it can be used by both gfs2 and ocfs2.

Signed-off-by: David Teigland <teigland@redhat.com>
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index b3d9ccd..376fc97 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -100,7 +100,7 @@
 header-y += jffs2.h
 header-y += keyctl.h
 header-y += limits.h
-header-y += lock_dlm_plock.h
+header-y += dlm_plock.h
 header-y += magic.h
 header-y += major.h
 header-y += matroxfb.h