Add level_zero to liboffload platforms

Author: adurang

offload/liboffload/API/Platform.td

@@ -27,6 +27,7 @@ def ol_platform_backend_t : Enum {
     Etor<"UNKNOWN", "The backend is not recognized">,
     Etor<"CUDA", "The backend is CUDA">,
     Etor<"AMDGPU", "The backend is AMDGPU">,
+    Etor<"LEVEL_ZERO", "The backend is Level Zero">,
     Etor<"HOST", "The backend is the host">,
   ];
 }

offload/liboffload/src/OffloadImpl.cpp

@@ -231,6 +231,8 @@ constexpr ol_platform_backend_t pluginNameToBackend(StringRef Name) {
     return OL_PLATFORM_BACKEND_AMDGPU;
   } else if (Name == "cuda") {
     return OL_PLATFORM_BACKEND_CUDA;
+  } else if (Name == "level_zero") {
+    return OL_PLATFORM_BACKEND_LEVEL_ZERO;
   } else {
     return OL_PLATFORM_BACKEND_UNKNOWN;
   }