doc: board: qemu-ppce500: Document eTSEC usage

Document how to launch a QEMU session with eTSEC as a network device.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
1 file changed