PM / Hibernate: Create a Radix-Tree to store memory bitmap

This patch adds the code to allocate and build the radix
tree to store the memory bitmap. The old data structure is
left in place until the radix tree implementation is
finished.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>