[TableGen] Remove unnecessary const_cast. NFC

llvm/utils/TableGen/DecoderEmitter.cpp

diff --git a/llvm/utils/TableGen/DecoderEmitter.cpp b/llvm/utils/TableGen/DecoderEmitter.cpp
index 24394a3..1a58672 100644
--- a/llvm/utils/TableGen/DecoderEmitter.cpp
+++ b/llvm/utils/TableGen/DecoderEmitter.cpp
@@ -249,7 +249,7 @@
         Bits.push_back(BI->getBit(Idx));
       }
     } else if (const BitInit *BI = dyn_cast<BitInit>(SI.Value)) {
-      Bits.push_back(const_cast<BitInit *>(BI));
+      Bits.push_back(BI);
     } else {
       for (unsigned Idx = 0U; Idx < SI.BitWidth; ++Idx)
         Bits.push_back(UnsetInit::get(def.getRecords()));