IB/uverbs: Add WQ support

User space applications which use RSS functionality need to create
a work queue object (WQ). The lifetime of such an object is:
 * Create a WQ
 * Modify the WQ from reset to init state.
 * Use the WQ (by downstream patches).
 * Destroy the WQ.

These commands are added to the uverbs API.

Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@rimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>