Leave it be. Removing the dead, infected wood won't help.
In all trees, only the outer-most half inch or so of wood is actually alive. The heartwood is always dead, and is there only to support the tree.
That fungus is feeding only on the dead wood. It will not, and cannot, feed on living wood. All removing it and the dead wood would do is expose the wood further down to fungal infection and hasten the speed at which the trunk eventually hollows out. It would not benefit the tree in any way. Indeed, if you start cutting into living tissue, you only stand to potentially allow infection into the living part of the tree (not from this fungus, but from other organisms, like bacterial canker).
The fungus is not directly harmful to the tree, as it is only feeding on already dead wood. If the entire inside of the trunk rots out, this could cause indirect harm, as it would weaken the trunk and make it more likely to fall over in strong winds. However, if left alone it will take many years, more than a decade, to reach that point. And even then, there is no guarantee it will come to any harm. Trees can leave decades with hollow trunks.