lib/rbtree.c: fix typo in comment

Signed-off-by: John de la Garza <john@jjdev.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h
index 57e75ae..fb31765 100644
--- a/include/linux/rbtree.h
+++ b/include/linux/rbtree.h
@@ -51,7 +51,7 @@
 
 #define RB_EMPTY_ROOT(root)  ((root)->rb_node == NULL)
 
-/* 'empty' nodes are nodes that are known not to be inserted in an rbree */
+/* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
 #define RB_EMPTY_NODE(node)  \
 	((node)->__rb_parent_color == (unsigned long)(node))
 #define RB_CLEAR_NODE(node)  \