remove struct uclass_driver::ops

Each _device_ belonging to a given uclass of course has its own ->ops,
of a type determined by and known to the uclass.

However, no instance of a uclass_driver seems to populate ->ops, and
the only reference to it in code is this relocation.

Moreover, it's not really clear what could sensibly be assigned; it
would have to be some "struct uclass_ops *" providing a set of methods
for the core to call on that particular uclass, but should the need
for that ever arise, it would be better to have a member of that
particular type instead of void*.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>