[mlir] Fix some of the warnings in MLIR code.

Summary:
* extra ';' in the following files:
    mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp
    mlir/lib/Dialect/Shape/IR/Shape.cpp

* base class ‘mlir::ConvertVectorToSCFBase<ConvertVectorToSCFPass>’
  should be explicitly initialized in the copy constructor [-Wextra] in
    mlir/lib/Conversion/VectorToSCF/VectorToSCF.cpp

* warning: ‘bool Expression::operator==(const Expression&) const’
  defined but not used [-Wunused-function] in
    mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-gen.cpp

Differential Revision: https://reviews.llvm.org/D81673