RDMA/rxe: Remove the is_user members of struct rxe_sq/rxe_rq/rxe_srq

The is_user members of struct rxe_sq/rxe_rq/rxe_srq are unsed since
commit ae6e843f ("RDMA/rxe: Add memory barriers to kernel queues").
In this case, it is fine to remove them directly.

Link: https://lore.kernel.org/r/20210930094813.226888-2-yangx.jy@fujitsu.com


Signed-off-by: Xiao Yang <yangx.jy@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>