NFSD: Add support for NFS v4.2 operation checking

The server does allow NFS over v4.2, even if it doesn't add any new
operations yet.

I also switch to using constants to represent the last operation for
each minor version since this makes the code cleaner and easier to
understand at a quick glance.

Signed-off-by: Anna Schumaker <bjschuma@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index e36dee5..737e40e 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -118,6 +118,9 @@
 
 #define FIRST_NFS4_OP	OP_ACCESS
 #define LAST_NFS4_OP 	OP_RECLAIM_COMPLETE
+#define LAST_NFS40_OP	OP_RELEASE_LOCKOWNER
+#define LAST_NFS41_OP	OP_RECLAIM_COMPLETE
+#define LAST_NFS42_OP	OP_RECLAIM_COMPLETE
 
 enum nfsstat4 {
 	NFS4_OK = 0,