NFS: Undo changes to idmap.h

When compiled without NFS v4 configured these function won't be defined
and the compiler will yell.

Signed-off-by: Bryan Schumaker <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

include/linux/nfs_idmap.h

···
 struct nfs_fattr;
 struct nfs4_string;
 
+#ifdef CONFIG_NFS_V4
 int nfs_idmap_init(void);
 void nfs_idmap_quit(void);
+#else
+static inline int nfs_idmap_init(void)
+{
+	return 0;
+}
+
+static inline void nfs_idmap_quit(void)
+{}
+#endif
+
 int nfs_idmap_new(struct nfs_client *);
 void nfs_idmap_delete(struct nfs_client *);