ethdev: rename physical port item in flow API

ethdev: rename physical port item in flow API

While RTE_FLOW_ITEM_TYPE_PORT refers to physical ports of the underlying
device using specific identifiers, these are often confused with DPDK port
IDs exposed to applications in the global name space.

Since this pattern item is seldom used, rename it RTE_FLOW_ITEM_PHY_PORT
for better clarity.

No ABI impact.

Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>