net/ena: fix queues number calculation

BugLink: http://bugs.launchpad.net/bugs/1664312

The ENA driver tries to open a queue per vCPU.
To determine how many vCPUs the instance have it uses num_possible_cpus()
while it should have use num_online_cpus() instead.
Signed-off-by: Netanel Belgazal <netanel@annapurnalabs.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 6a1ce2fb)
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -2667,7 +2667,7 @@ static int ena_calc_io_queue_num(struct pci_dev *pdev,
 		io_sq_num = get_feat_ctx->max_queues.max_sq_num;
 	}
 
-	io_queue_num = min_t(int, num_possible_cpus(), ENA_MAX_NUM_IO_QUEUES);
+	io_queue_num = min_t(int, num_online_cpus(), ENA_MAX_NUM_IO_QUEUES);
 	io_queue_num = min_t(int, io_queue_num, io_sq_num);
 	io_queue_num = min_t(int, io_queue_num,
 			     get_feat_ctx->max_queues.max_cq_num);