[PATCH] ppc64: More U3 device-tree fixes

Some more U3 revisions have the missing "interrupts" property in U3,
this adds them to the fixup code in prom_init.c

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>