idpf: call set_real_num_queues in idpf_open

On initial driver load, alloc_etherdev_mqs is called with whatever max
queue values are provided by the control plane. However, if the driver
is loaded on a system where num_online_cpus() returns less than the max
queues, the netdev will think there are more queues than are actually
available. Only num_online_cpus() will be allocated, but
skb_get_queue_mapping(skb) could possibly return an index beyond the
range of allocated queues. Consequently, the packet is silently dropped
and it appears as if TX is broken.

Set the real number of queues during open so the netdev knows how many
queues will be allocated.

Fixes: 1c325aac ("idpf: configure resources for TX queues")
Signed-off-by: Joshua Hay <joshua.a.hay@intel.com>
Reviewed-by: Madhu Chittim <madhu.chittim@intel.com>
Tested-by: Samuel Salin <Samuel.salin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>