lib: memory alloc

Add a generic library (which uses genalloc) that manages
pools of contiguous memory.

APIs are provided to allocate (and if desired map) and free
memory, as well to initialize a memory pool.

Change-Id: I75deda08eb852a323b4d1a32c3b7980e7aa143a8
Signed-off-by: Larry Bassel <lbassel@codeaurora.org>
(cherry picked from commit 54bff5255ff4adf204d2b4a9805cdb998167fb9e)