net/mlx5: add indexed memory pool

net/mlx5: add indexed memory pool

Currently, the memory allocated by rte_malloc() also introduced more
than 64 bytes overhead. It means when allocate 64 bytes memory, the
real cost in memory maybe double. And the libc malloc() overhead is 16
bytes, If users try allocating millions of small memory blocks, the
overhead costing maybe huge. And save the memory pointer will also be
quite expensive.

Indexed memory pool is introduced to save the memory for allocating
huge amount of small memory blocks. The indexed memory uses trunk and
bitmap to manage the memory entries. While the pool is empty, the trunk
slot contains memory entry array will be allocated firstly. The bitmap
in the trunk records the entry allocation. The offset of trunk slot in
the pool and the offset of memory entry in the trunk slot compose the
index for the memory entry. So, by the index, it will be very easy to
address the memory of the entry. User saves the 32 bits index for the
memory resource instead of the 64 bits pointer.
User should create different pools for allocating different size of
small memory block. It means one pool provides one fixed size of small
memory blocked allocating.

Signed-off-by: Suanming Mou <suanmingm@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>