IB/uverbs: Expose XRQ capabilities

Make XRQ capabilities available via ibv_query_device() verb.

Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com>
Reviewed-by: Yossi Itigin <yosefe@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>