[clang] [llvm] [NFC] [RISCV] Refactor class RISCVExtension (PR #120040)

[Pengcheng Wang via cfe-commits]

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@@ -12,21 +12,32 @@
 
 // Subclass of SubtargetFeature to be used when the feature is also a RISC-V
 // extension. Extensions have a version and may be experimental.
+// NOTE: The extension name must start with
+//       - "FeatureStdExt" for standard extensions
+//       - "FeatureVendor" for vendor-specific extensions
 //
-// name      - Name of the extension in lower case.
 // major     - Major version of extension.
 // minor     - Minor version of extension.
-// desc      - Description of extension.
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wangpc-pp wrote:

We still need `desc` parameter.

https://github.com/llvm/llvm-project/pull/120040