verify-uselistorder: Change the default -num-shuffles=5

Change the default for `-num-shuffles` to 5 and better document the
algorithm in the header docs of `verify-uselistorder`.

llvm-svn: 214419
diff --git a/llvm/test/Bitcode/attributes.ll b/llvm/test/Bitcode/attributes.ll
index 8286e39..1543558 100644
--- a/llvm/test/Bitcode/attributes.ll
+++ b/llvm/test/Bitcode/attributes.ll
@@ -1,5 +1,5 @@
 ; RUN: llvm-as < %s | llvm-dis | FileCheck %s
-; RUN: verify-uselistorder < %s -preserve-bc-use-list-order -num-shuffles=5
+; RUN: verify-uselistorder < %s -preserve-bc-use-list-order
 ; PR12696
 
 define void @f1(i8 zeroext)