Some uses of TOSA rely on the constant operands of particular operations,
e.g. paddings and pad_const in pad op. Add a verification pattern in the
validation pass, and this is optionally enabled.
Change-Id: I1628c0840a27ab06ef91150eee56ad4f5ac9543d
Typically you don't want to define a default implementation for a virtual function in this case as it is expected to be overrideen.