RDMA/rtrs: Fix warning when use poll mode on client side.

RDMA/rtrs: Fix warning when use poll mode on client side.

When testing with poll mode, it will fail and lead to warning below on
client side:

$ echo "sessname=bla path=gid:fe80::2:c903:4e:d0b3@gid:fe80::2:c903:8:ca17 device_path=/dev/nullb2 nr_poll_queues=-1" | \
  sudo tee /sys/devices/virtual/rnbd-client/ctl/map_device

rnbd_client L597: Mapping device /dev/nullb2 on session bla, (access_mode: rw, nr_poll_queues: 8)
WARNING: CPU: 3 PID: 9886 at drivers/infiniband/core/cq.c:447 ib_cq_pool_get+0x26f/0x2a0 [ib_core]

The problem is in case of poll queue, we need to still call
ib_alloc_cq/ib_free_cq, we can't use cq_poll api for poll queue.

As both client and server use shared function from rtrs, set irq_con_num
to con_num on server side, which is number of total connection of the
session, this way we can differ if the rtrs_con requires pollqueue.

Following up patches will replace the duplicate code with helpers.

Link: https://lore.kernel.org/r/20210922125333.351454-4-haris.iqbal@ionos.com
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Reviewed-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>