net: Provide MemReentrancyGuard * to qemu_new_nic()

net: Provide MemReentrancyGuard * to qemu_new_nic()

Recently MemReentrancyGuard was added to DeviceState to record that the
device is engaging in I/O. The network device backend needs to update it
when delivering a packet to a device.

In preparation for such a change, add MemReentrancyGuard * as a
parameter of qemu_new_nic().

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Signed-off-by: Jason Wang <jasowang@redhat.com>
(cherry picked from commit 7d0fefdf81f5973334c344f6b8e1896c309dff66)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
(Mjt: fixup in hw/net/xen_nic.c due to lack of v8.1.0-2771-g25967ff69f
 "hw/xen: update Xen PV NIC to XenDevice model")