IB/uverbs: Delete type and id from uverbs_obj_attr

In this context the uobject is not allowed to be NULL, so type is the same
as uobject->type, and at least for IDR, id is the same as uobject->id.

FD objects should never handle the FD number outside the uAPI boundary
code.

Suggested-by: Guy Levi <guyle@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>