[MLIR][Arith] SelectOp fix invalid folding

The pattern `select %x, true, false => %x` is only valid in case that the return type is identical to the type of `%x` (i.e., i1).
Hence, the check `isInteger(1)` was replaced with `isSignlessInteger(1)`.

Author: 7FM

mlir/lib/Dialect/Arith/IR/ArithOps.cpp

@@ -2314,7 +2314,8 @@ OpFoldResult arith::SelectOp::fold(FoldAdaptor adaptor) {
     return trueVal;
 
   // select %x, true, false => %x
-  if (getType().isInteger(1) && matchPattern(adaptor.getTrueValue(), m_One()) &&
+  if (getType().isSignlessInteger(1) &&
+      matchPattern(adaptor.getTrueValue(), m_One()) &&
       matchPattern(adaptor.getFalseValue(), m_Zero()))
     return condition;