RDMA/rxe: Fix unsafe drain work queue code

RDMA/rxe: Fix unsafe drain work queue code

If create_qp does not fully succeed it is possible for qp cleanup
code to attempt to drain the send or recv work queues before the
queues have been created causing a seg fault. This patch checks
to see if the queues exist before attempting to drain them.

Link: https://lore.kernel.org/r/20230620135519.9365-3-rpearsonhpe@gmail.com
Reported-by: syzbot+2da1965168e7dbcba136@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-rdma/00000000000012d89205fe7cfe00@google.com/raw
Fixes: 49dc9c1f0c7e ("RDMA/rxe: Cleanup reset state handling in rxe_resp.c")
Fixes: fbdeb828a21f ("RDMA/rxe: Cleanup error state handling in rxe_comp.c")
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>