net: add missing endianness annotations

OVS currently maintains a copy of those headers with the right endianness
annotations so that sparse checks can pass.

We introduced rte_beXX_t for better readibility in v17.08.
Let's make use of them, OVS then only needs to override those rte_beXX_t
types by exposing a tweaked rte_byteorder.h header.

Other existing dpdk users won't be affected since rte_beXX_t types are
mapped to uintXX_t types.

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>