Fix create WQ to use the given user handle, in addition dropped some
duplicated code from this flow.

Fixes: fd3c7904 ("IB/core: Change idr objects to use the new schema")
Fixes: f213c052 ("IB/uverbs: Add WQ support")
Link: https://lore.kernel.org/r/20200506082444.14502-9-leon@kernel.orgSigned-off-by: NYishai Hadas <yishaih@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>