passthrough: Fix duplicated MAC addr when multi-port NIC assigned to HVM domain

passthrough: Fix duplicated MAC addr when multi-port NIC assigned to HVM domain

This patch fixes duplicated MAC address when multi-port NIC is
assigned to HVM domain.

Currently multi-function device is shown as two single function
devices. e1000e driver and igb driver for linux add 1 to MAC address of
second port of multi-port NIC. But they don't add 1 to MAC address of
second port if NIC is single-function device. Because of this, the MAC
addresses of the first port and the second port are duplicated.

The patch make Header Type register passthrough-type. This means a
multi-function device is shown as two multi-function devices which
implement only one function. So e1000e driver and igb driver add 1 to
MAC address of second port.

When we use windows guest, the same issue occurs, the patch fix it.

Signed-off-by: Yuji Shimada <shimada-yxb@necst.nec.co.jp>