[POWERPC] Don't crash on cell with 2 BEs when !CONFIG_NUMA

The SPU code will crash if CONFIG_NUMA is not set and SPUs are found on
a non-0 node. This workaround will ignore those SPEs and just print an
message in the kernel log.

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