Future devices we will be adding to the pseries machine (e.g. PCI) will
need nodes in the device tree which explicitly reference the top-level
interrupt controller via interrupt-parent or interrupt-map properties.

In order to do this, the interrupt controller node needs an assigned
phandle.  This patch adds the appropriate property, in preparation.
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAlexander Graf <agraf@suse.de>