[fuchsia] Use virtio-net-pci for both ARM64 and x64 emulation.

There is no longer a need to use E1000 under x64, and Fuchsia defaults
to virtio-net-pic for both architectures.

Bug: fuchsia:59041
Change-Id: I817bc69e84e4b024db6b9e3d8ee8fabe2502a552
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2379718Reviewed-by: David Dorwin <ddorwin@chromium.org>
Auto-Submit: Wez <wez@chromium.org>
Commit-Queue: David Dorwin <ddorwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802343}

build/fuchsia/qemu_target.py

@@ -102,15 +102,14 @@ class QemuTarget(emu_target.EmuTarget):
       emu_command.extend([
           '-machine','virt,gic_version=3',
       ])
-      netdev_type = 'virtio-net-pci'
     else:
       emu_command.extend([
           '-machine', 'q35',
       ])
-      netdev_type = 'e1000'
 
     # Configure virtual network. It is used in the tests to connect to
     # testserver running on the host.
+    netdev_type = 'virtio-net-pci'
     netdev_config = 'user,id=net0,net=%s,dhcpstart=%s,host=%s' % \
             (GUEST_NET, GUEST_IP_ADDRESS, HOST_IP_ADDRESS)