Minimal VFS additions

This patch simply removes the place holder vfs_t type and includes
some generic Linux VFS headers.  It also makes some minor fid_t
additions for compatibility.

include/sys/vfs.h

@@ -25,9 +25,12 @@
 #ifndef _SPL_ZFS_H
 #define _SPL_ZFS_H
 
-typedef struct vfs {
-	int foo;
-} vfs_t;
+#include <linux/mount.h>
+#include <linux/fs.h>
+#include <linux/dcache.h>
+#include <linux/statfs.h>
+#include <linux/xattr.h>
+#include <linux/security.h>
 
 #define	MAXFIDSZ	64
 
@@ -41,4 +44,7 @@ typedef struct fid {
 	} un;
 } fid_t;
 
+#define	fid_len		un._fid.len
+#define	fid_data	un._fid.data
+
 #endif /* SPL_ZFS_H */