[ARM64] Adds Cortex-A53 and Cortex-A57 as known cpus for ARM64.

[cestes]

Summary

ARM64TargetInfo::setCPU() checks for known CPUs in the ARM64
backend. This patch adds cortex-a53 and cortex-a57 as known options.

[t.p.northover]

Hi Dave,

I think this one is duplicating a recent commit by James (a couple of lines above your additions).

Cheers.

Tim.

lib/Basic/Targets.cpp

virtual bool setABI(const std::string &Name) {
     return true;
   }
 
   virtual bool setCPU(const std::string &Name) {
     bool CPUKnown = llvm::StringSwitch<bool>(Name)
                         .Case("generic", true)
                         .Cases("cortex-a53", "cortex-a57", true)
                         .Case("cyclone", true)
+                        .Case("cortex-a53", true)
+                        .Case("cortex-a57", true)
                         .Default(false);
     return CPUKnown;
   }
 
   virtual void getTargetDefines(const LangOptions &Opts,
                                 MacroBuilder &Builder) const {
     // Target identification.
     Builder.defineMacro("__aarch64__");