wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/utimes.c b/fs/utimes.c
index aa138d6..85c40f4 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -103,9 +103,9 @@
 		}
 	}
 retry_deleg:
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	error = notify_change(path->dentry, &newattrs, &delegated_inode);
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	if (delegated_inode) {
 		error = break_deleg_wait(&delegated_inode);
 		if (!error)