s/comparision/comparison/.

I typoed this word and then auto-complete duplicated it all over the
place. This change fixes all the comments.

This change has no semantic effect (comment only).

Change-Id: I8952e9e71302043574757cd74a05e66500008432
diff --git a/crypto/ex_data_impl.c b/crypto/ex_data_impl.c
index db811d4..cac1daa 100644
--- a/crypto/ex_data_impl.c
+++ b/crypto/ex_data_impl.c
@@ -151,7 +151,7 @@
   return a->class_value;
 }
 
-/* class_cmp is a comparision function for an LHASH of |EX_CLASS_ITEM|
+/* class_cmp is a comparison function for an LHASH of |EX_CLASS_ITEM|
  * structures. */
 static int class_cmp(const EX_CLASS_ITEM *a, const EX_CLASS_ITEM *b) {
   return a->class_value - b->class_value;