[POWERPC] spufs: support new OF device tree format

The properties we used traditionally in the device tree are somewhat
nonstandard.  This adds support for a more conventional format using
'interrupts' and 'reg' properties.

The interrupts are specified in three cells (class 0, 1 and 2) and
registered at the interrupt-parent.

The reg property contains either three or four register areas in the
order 'local-store', 'problem', 'priv2', and 'priv1', so the priv1 one
can be left out in case of hypervisor driven systems that access these
through hcalls.

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>