virtio: fix memory leak of virtqueue memzones

When virtio was proposed in DPDK, there is no API to free memzones.
But this has changed since rte_memzone_free() has been implemented by
commit ff909fe21f0a ("mem: introduce memzone freeing").

This patch is to make sure memzones in struct virtqueue, like mz and
virtio_net_hdr_mz, are freed when queue is released or setup fails.

Fixes: c1f86306a026 ("virtio: add new driver")

Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>