Fix typos concerning hierarchy

        heirarchical, hierachical -> hierarchical
        heirarchy, hierachy -> hierarchy

Signed-off-by: Uwe Kleine-König <zeisberg@informatik.uni-freiburg.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 2627909..e86c37c 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -154,7 +154,7 @@
  * characteristics relative to its multiple connections.  We ignore
  * this for now.  We also assume that all cpu and memory sets have
  * their distances represented at a common level.  This won't be
- * true for heirarchical NUMA.
+ * true for hierarchical NUMA.
  *
  * In any case the ibm,associativity-reference-points should give
  * the correct depth for a normal NUMA system.