RDMA/rxe: Add rxe_is_fenced() subroutine

RDMA/rxe: Add rxe_is_fenced() subroutine

The code thc that decides whether to defer execution of a wqe in
rxe_requester.c is isolated into a subroutine rxe_is_fenced() and removed
from the call to req_next_wqe(). The condition whether a wqe should be
fenced is changed to comply with the IBA. Currently an operation is fenced
if the fence bit is set in the wqe flags and the last wqe has not
completed. For normal operations the IBA actually only requires that the
last read or atomic operation is complete.

Link: https://lore.kernel.org/r/20220630190425.2251-2-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>