As stated above you can force the mapping of any nic to a specified ethX interface. once you have made sure you have the appropriate ifcfg-ethX script (and a set MAC) you can use udev to force the OS to map the mlx device and the ethX HCA :
/etc/udev/rules.d/70-persistent-net.rules:
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:02:c9:12:86:90", ATTR{type}=="1", KERNEL=="eth*", NAME="eth4"
Reboot.