kvm tools: Set correct virtio pci device class code

kvm tools: Set correct virtio pci device class code

All the virtio pci device is set to class code 0x010000, this is wrong.
This patch sets the correct class code and makes lspci report correct
class type. For example, the net device:

Before:
$ lspci
00:03.0 SCSI storage controller: Red Hat, Inc Virtio network device

After:
$ lspci
00:03.0 Ethernet controller: Red Hat, Inc Virtio network device

Acked-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Asias He <asias.hejun@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>