[Alignment][NFC] CreateMemSet use MaybeAlign

Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

Reviewers: courbet

Subscribers: arsenm, jvesely, nhaehnle, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D71213
diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index d07aaf5..149982d 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -350,7 +350,7 @@
   CGF.Builder.CreateMemSet(
       addr, llvm::ConstantInt::get(CGF.Int8Ty, 0),
       CGF.getContext().toCharUnitsFromBits(AtomicSizeInBits).getQuantity(),
-      LVal.getAlignment().getQuantity());
+      LVal.getAlignment().getAsAlign());
   return true;
 }