[mlir][VectorOps] Fix more GCC5 weirdness

VectorToSCF.cpp:515:47: error: specialization of 'template<class TransferOpTy> mlir::LogicalResult mlir::VectorTransferRewriter<TransferOpTy>::matchAndRewrite(mlir::Operation*, mlir::PatternRewriter&) const' in different namespace [-fpermissive]