[GFS2] Export lm_interface to kernel headers


lm_interface.h has a few out of the tree clients such as GFS1
and userland tools.

Right now, these clients keeps a copy of the file in their build tree
that can go out of sync.

Move lm_interface.h to include/linux, export it to userland and
clean up fs/gfs2 to use the new location.

Signed-off-by: Fabio M. Di Nitto <fabbione@ubuntu.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/locking.c b/fs/gfs2/locking.c
index 65eca48..663fee7 100644
--- a/fs/gfs2/locking.c
+++ b/fs/gfs2/locking.c
@@ -16,8 +16,7 @@
 #include <linux/kmod.h>
 #include <linux/fs.h>
 #include <linux/delay.h>
-
-#include "lm_interface.h"
+#include <linux/lm_interface.h>
 
 struct lmh_wrapper {
 	struct list_head lw_list;