Refactor related objects to use their own asynchronous event FD.
The ufile event FD will be the default in case an object won't have its own
event FD.

Link: https://lore.kernel.org/r/20200519072711.257271-3-leon@kernel.orgSigned-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>