[Offload] Add default for HSA agent type to silence warning (#145943)

Summary:
There's a new one called the AIE (AI Engine). We could handle this, but
since we don't use it currently I'm just making it future-proof. Adding
the AIE check would require checking the HSA version which isn't
worthwhile just yet.

offload/plugins-nextgen/amdgpu/src/rtl.cpp

@@ -2591,6 +2591,9 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
       case HSA_DEVICE_TYPE_DSP:
         TmpCharPtr = "DSP";
         break;
+      default:
+        TmpCharPtr = "Unknown";
+        break;
       }
       Info.add("Device Type", TmpCharPtr);
     }