[POWERPC] 86xx: Cleaned up platform dts files

* Removed explicit linux,phandle usage. Use references and labels now
* Removed interrupts property from openpic node
* Removed interrupt-parent property from openpic node that pointed to itself

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Jon Loeliger <jdl@freescale.com>