NFS: Use proper naming conventions for nfs_client.impl_id field

Clean up:  When naming fields and data types, follow established
conventions to facilitate accurate grep/cscope searches.

Additionally, for consistency, move the impl_id field into the NFSv4-
specific part of the nfs_client, and free that memory in the logic
that shuts down NFSv4 nfs_clients.

Introduced by commit 7d2ed9ac "NFSv4: parse and display server
implementation ids," Fri Feb 17, 2012.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 900d733..773e021 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -81,13 +81,13 @@
 	u32			cl_exchange_flags;
 	struct nfs4_session	*cl_session;	/* shared session */
 	struct nfs41_server_scope *cl_serverscope;
+	struct nfs41_impl_id	*cl_implid;
 #endif /* CONFIG_NFS_V4 */
 
 #ifdef CONFIG_NFS_FSCACHE
 	struct fscache_cookie	*fscache;	/* client index cache cookie */
 #endif
 
-	struct nfs41_impl_id	*impl_id;	/* from exchange_id */
 	struct net		*net;
 };