[TableGen] Fix CodeGenRegisterClass::hasType for simple-type arguments

The `hasType` function may be given a type that has been modified from
its original form (in particular made "simple", due to a predicate).
Make sure that such a type is still recognized as associated with a
register class, if the class contains it under any hw-mode.
This is somewhat optimistic though, since there is no information as
to where that simple type originated from.