[make] Update QEMU_OPTS in Makefile

- Increase memory from default 128M to 256M. The network buffers in osboot
  allocate 128M+16M and were failing with the default 128M QEMU allocates.
- Use e1000 for the built in networking device.
- If the host has an ASIX usb eth dongle connected then disconnect it and pass
  it through to QEMU. This requires write permissions set up by the udev rules
  provided in scripts/99-asix.rules.

Change-Id: I3ea4fcf953f1627b8a32c8ac4ca66f61dbf2fbc8
1 file changed