mempool: add non-IO flag

mempool: add non-IO flag

Mempool is a generic allocator that is not necessarily used
for device IO operations and its memory for DMA.
Add MEMPOOL_F_NON_IO flag to mark such mempools automatically
a) if their objects are not contiguous;
b) if IOVA is not available for any object.
Other components can inspect this flag
in order to optimize their memory management.

Discussion: https://mails.dpdk.org/archives/dev/2021-August/216654.html

Signed-off-by: Dmitry Kozlyuk <dkozlyuk@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>
Reviewed-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>