kvm tools: Add MMIO address mapper

When we have a MMIO exit, we need to find which device
has registered to use the accessed MMIO space.

The mapper maps ranges of guest physical addresses to
callback functions.

Implementation is based on an interval red-black tree.

Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>