Update Btrfs files for in-kernel usage

btrfs had magic to put the chagneset id into a printk on module load.
This removes that from the Makefile and hardcodes the printk to print
"Btrfs"

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/version.h b/fs/btrfs/version.h
new file mode 100644
index 0000000..9bf3946
--- /dev/null
+++ b/fs/btrfs/version.h
@@ -0,0 +1,4 @@
+#ifndef __BTRFS_VERSION_H
+#define __BTRFS_VERSION_H
+#define BTRFS_BUILD_VERSION "Btrfs"
+#endif