validation: pktio check for number of interfaces
validation: pktio check for number of interfaces

CI got following error:
pktio.c: In function 'pktio_test_recv_queue':
pktio.c:643:11: error: 'pktio[0]' may be used uninitialized
	in this function [-Werror=maybe-uninitialized]
  pktio_tx = pktio[0]

That can never happen due to num_ifaces always > 1 in our test.
Add special check for that to make new gcc happy.

Signed-off-by: Maxim Uvarov <db4d16e02ae2d7493db430203537da8b2e34f290@linaro.org>
Reviewed-by: Christophe Milard <99616a981fa4477cda708a70f78076761c0c9f1c@linaro.org>

nmorey/odp,ravineet-singh/odp,erachmi/odp,mike-holmes-linaro/odp,erachmi/odp,dkrot/odp,rsalveti/odp,erachmi/odp,dkrot/odp,rsalveti/odp,ravineet-singh/odp,mike-holmes-linaro/odp,nmorey/odp,dkrot/odp,rsalveti/odp,mike-holmes-linaro/odp,rsalveti/odp,nmorey/odp,ravineet-singh/odp,dkrot/odp,erachmi/odp,rsalveti/odp,ravineet-singh/odp,mike-holmes-linaro/odp,nmorey/odp