[HIP] Make the HIP default architecture use the enum value

Summary:
This default enum is used in other places, we should keep it consistent.

Author: jhuber6

clang/include/clang/Basic/Cuda.h

@@ -123,7 +123,7 @@ enum class CudaArch {
   LAST,
 
   CudaDefault = CudaArch::SM_52,
-  HIPDefault = CudaArch::GFX803,
+  HIPDefault = CudaArch::GFX906,
 };
 
 static inline bool IsNVIDIAGpuArch(CudaArch A) {

clang/lib/Driver/Driver.cpp

@@ -3373,7 +3373,7 @@ class OffloadingActionBuilder final {
                      const Driver::InputList &Inputs)
         : CudaActionBuilderBase(C, Args, Inputs, Action::OFK_HIP) {
 
-      DefaultCudaArch = CudaArch::GFX906;
+      DefaultCudaArch = CudaArch::HIPDefault;
 
       if (Args.hasArg(options::OPT_fhip_emit_relocatable,
                       options::OPT_fno_hip_emit_relocatable)) {