Teach clang driver about Cortex-A53 and Cortex-A57.

Adds some Cortex-A53 strings where they were missing before.
Cortex-A57 is entirely new to clang.

Doesn't touch code only used by Darwin, in consequence of which
one of the A53 lines has been removed.

Change-Id: I5edb58f6eae93947334787e26a8772c736de6483

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193364 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChain.cpp b/lib/Driver/ToolChain.cpp
index 7a2d23d..e21dd06 100644
--- a/lib/Driver/ToolChain.cpp
+++ b/lib/Driver/ToolChain.cpp
@@ -245,7 +245,7 @@
     .Case("cortex-m4", "v7em")
     .Case("cortex-a9-mp", "v7f")
     .Case("swift", "v7s")
-    .Case("cortex-a53", "v8")
+    .Cases("cortex-a53", "cortex-a57", "v8")
     .Default("");
 }