net/virtio: fix crash when number of virtio devices > 1

The vtpci_ops assignment needs the 'hw->port_id' as an input parameter.
That said, we should set 'hw->port_id' firstly, then do the vtpci_ops
assignment, while the code does reversely. That would result to a crash
when more than one virtio devices are used, because we keep assigning
proper vtpci_ops to virtio_hw_internal[0]->vtpci_ops, leaving the pointer
for other ports being NULL.

Reverse the order fixes this issue.

Fixes: 9470427c88e1 ("net/virtio: do not store PCI device pointer at shared memory")
Cc: stable@dpdk.org
Reported-by: Lei Yao <lei.a.yao@intel.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>