RDMA/core: Simplify type usage for ib_uverbs_async_handler()

This function works on an ib_uverbs_async_file. Accept that as a parameter
instead of the struct ib_uverbs_file.

Consoldiate all the callers working from an ib_uevent_object to a single
function and locate the async_file directly from the struct ib_uobject
instead of using context_ptr.

Link: https://lore.kernel.org/r/1578504126-9400-11-git-send-email-yishaih@mellanox.com


Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>