net/vmxnet3: return correct value for VMXNET3_CMD_GET_DEV_EXTRA_INFO

net/vmxnet3: return correct value for VMXNET3_CMD_GET_DEV_EXTRA_INFO

VMXNET3_CMD_GET_DEV_EXTRA_INFO should return 0 for emulation
mode

This behavior can be observed by the following steps:

1) run a Linux distro on esxi server (5.x+)
2) modify vmxnet3 Linux driver to read the register:

  VMXNET3_WRITE_BAR1_REG(adapter, VMXNET3_REG_CMD, VMXNET3_CMD_GET_DEV_EXTRA_INFO);
  ret =  VMXNET3_READ_BAR1_REG(adapter, VMXNET3_REG_CMD);
  pr_info("vmxnet3 dev_info: 0x%x\n", ret);

The kernel log will have some like the following message:

  [ 7005.111170] vmxnet3 dev_info: 0x0

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Dmitry Fleytman <dmitry@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>