[clang] [llvm] [NFC][HLSL][DirectX] Let `HLSLRootSignature` reuse the `dxbc` defined enums (PR #145986)

[Justin Bogner via llvm-commits]

================
@@ -56,7 +56,7 @@ TEST(HLSLRootSignatureTest, DescriptorUAVClauseDump) {
   Clause.NumDescriptors = 3298;
   Clause.Space = 932847;
   Clause.Offset = 1;
-  Clause.Flags = DescriptorRangeFlags::ValidFlags;
+  Clause.Flags = llvm::dxbc::DescriptorRangeFlags(0x1000f);
----------------
bogner wrote:

Should we `or` enum values together here as well? Also applies to a couple of places later in this file.

https://github.com/llvm/llvm-project/pull/145986