Fix a use of LLVM_FALLTHROUGH that wasn't even in a switch.

I was over-aggressive in my conversions from comments to the
fallthrough attribute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278903 91177308-0d34-0410-b5e6-96231b3b80d8

lib/TableGen/TGParser.cpp

@@ -1286,7 +1286,6 @@ Init *TGParser::ParseSimpleValue(Record *CurRec, RecTy *ItemType,
           continue;
         }
         // Fallthrough to try convert this to a bit.
-        LLVM_FALLTHROUGH;
       }
       // All other values must be convertible to just a single bit.
       Init *Bit = Vals[i]->convertInitializerTo(BitRecTy::get());