[POWERPC] Fix cell "new style" mapping and add debug

This fixes a typo in the "new style" code for mapping SPE resources,
which causes it to try to map the same resource 4 times.

It also adds some pr_debug's that are useful to track down issues with
the firmware when bringinh up new machines.

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