rxe_queue.h currently includes <uapi/rdma/rdma_user_rxe.h> for a
definition of struct rxe_queue_buf. But it is only used as a pointer so
the definition is not needed.

This patch replaces the include statement with the declaration

     struct rxe_queue_buf;

Link: https://lore.kernel.org/r/20220630190425.2251-5-rpearsonhpe@gmail.comReported-by: NFrank Zago <frank.zago@hpe.com>
Signed-off-by: NBob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>