Moved from lib/librte_mempool, stack mempool handler is an independent
driver.
Shared builds would now require to link in librte_mempool_stack for
"stack" mempool handler.
Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
