Cleanup PPC64 unaligned i64 load/store

Remove an accidentally-added instruction definition and add a comment in the
test case. This is in response to a post-commit review by Bill Schmidt.

No functionality change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177404 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/PowerPC/unal4-std.ll b/test/CodeGen/PowerPC/unal4-std.ll
index dc4c20c..169bd78 100644
--- a/test/CodeGen/PowerPC/unal4-std.ll
+++ b/test/CodeGen/PowerPC/unal4-std.ll
@@ -17,6 +17,9 @@
 if.end210:                                        ; preds = %entry
   ret void
 
+; This will generate two align-1 i64 stores. Make sure that they are
+; indexed stores and not in r+i form (which require the offset to be
+; a multiple of 4).
 ; CHECK: @copy_to_conceal
 ; CHECK: stdx {{[0-9]+}}, 0,
 }