net/virtio: fix MSI-X for modern devices

net/virtio: fix MSI-X for modern devices

The field, use_msix, in struct virtio_hw is not updated for modern
device, and is always zero. And now we depend on the status feature
and MSI-X to report LSC support (which is also not a correct
behavior). As a result, LSC is always disabled for modern devices.

To fix this, we just recognize MSI-X capability when going through
capability list, and update the info in virtio.

Fixes: 6ba1f63b5ab0 ("virtio: support specification 1.0")
Cc: stable@dpdk.org
Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>