RDMA/rxe: Remove qp reference counting in tasks

RDMA/rxe: Remove qp reference counting in tasks

Currently each of the three tasklets requester, completer and responder in
the rxe driver take and release a reference to the qp argument at the
beginning and end of the subroutines. The caller passing in the qp
argument should be responsible for holding a reference to qp so these are
not required. Further doing so breaks the qp cleanup code in
rxe_qp_do_cleanup which calls these routines after all the references have
been dropped so they cannot drain the packet and work request queues as
intended.

In fact if these routines are deferred by calling tasklet_schedule there
is no guarantee that the calling code does have a qp reference.  That is a
bug in rxe_task.c which will be fixed later in this series.

Link: https://lore.kernel.org/r/20230304174533.11296-6-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>