[clang][RISCV] Extend intrinsic size check variable from 16 -> 32 bits. NFC

We currently have over 67000 intrinsics, uint16_t will overflow.

Author: 4vtomat

clang/lib/Sema/SemaRISCV.cpp

@@ -399,7 +399,7 @@ void RISCVIntrinsicManagerImpl::InitRVVIntrinsic(
                                      Record.HasFRMRoundModeOp);
 
   // Put into IntrinsicList.
-  uint16_t Index = IntrinsicList.size();
+  uint32_t Index = IntrinsicList.size();
   assert(IntrinsicList.size() == (size_t)Index &&
          "Intrinsics indices overflow.");
   IntrinsicList.push_back({BuiltinName, Signature});