Im afraid I dont know, nor do I know id it was ever said
why is being a wizard like being a drow? both are likely to find a dagger in the back from a rival or one looking to further his own goals, fame and power
It depends on whether a DM treats psionics as magic, as far as the rules are concerned, or not.
If yes then ghazneths are immune from psionics. If not then they wouldn't be.
Of course the whole reason for ghazneths to exist was to have an unkillable plot device for a good story, so I would assume ghazneths are immune and any attempt at mind control runs a serious risk of driving an attacking psionicist insane.
Look for me and my content at EN World (user name: sanishiver).