[LIBS] Minor improvement to reduce memory wasteage in buddy allocator

We all know that we waste lot of memory in buddy allocator because
buddy allocator always gives us memory in power of 2 which leads
to some wasteage in each memory allocation.

This patch attempts to reduce this wasteage by downgrading alloced
buddy area to smallest bin and freeing some extra blocks of smallest
size from alloced area.

Signed-off-by: Anup Patel <anup@brainfault.org>