[clang] [llvm] [RISCV][llvm] Support Smpmpmt version 0.6 (PR #166322)

[Craig Topper via cfe-commits]

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@@ -139,6 +139,7 @@ on support follow.
      ``Smepmp``        Supported
      ``Smmpm``         Supported
      ``Smnpm``         Supported
+     ``Smpmpmt``       Supported
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topperc wrote:

Should be in the experimental extension section with a link to the spec.

https://github.com/llvm/llvm-project/pull/166322