Move cpu_{sibling,core}_map into per-CPU space

Move cpu_{sibling,core}_map into per-CPU space

These cpu maps get read from all CPUs, so apart from addressing the
square(nr_cpus) growth of these objects, they also get moved into the
previously introduced read-mostly sub-section of the per-CPU section,
in order to not need to waste a full cacheline in order to align (and
properly pad) them, which would be undue overhead on systems with low
NR_CPUS.

Signed-off-by: Jan Beulich <jbeulich@novell.com>