ethdev: use hairpin helper functions

ethdev: use hairpin helper functions

Hairpin helper functions were not used by drivers, but it was used only
local to ethdev. They are:
'rte_eth_dev_is_rx_hairpin_queue()'
'rte_eth_dev_is_tx_hairpin_queue()'

Exposing them as internal APIs and update mlx5 driver (only user of
hairpin) to use them.

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
Acked-by: David Marchand <david.marchand@redhat.com>