ethdev: get supported mempool per port

ethdev: get supported mempool per port

Now that dpdk supports more than one mempool drivers and
each mempool driver works best for specific PMD, example:
- sw ring based mempool for Intel PMD drivers.
- dpaa2 HW mempool manager for dpaa2 PMD driver.
- fpa HW mempool manager for Octeontx PMD driver.

Application would like to know the best mempool handle
for any port.

Introducing rte_eth_dev_pool_ops_supported() API,
which allows PMD driver to advertise
his supported pool capability to the application.

Supported pools are categorized in below priority:-
- Best mempool handle for this port (Highest priority '0')
- Port supports this mempool handle (Priority '1')

Signed-off-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>