eal: introduce big and little endian types

eal: introduce big and little endian types

This commit introduces new rte_{le,be}{16,32,64}_t types and updates
rte_{le,be,cpu}_to_{le,be,cpu}_*() accordingly.

These types are added for documentation purposes, mainly to clarify the
byte ordering to use for storage when not CPU order. Doing so eliminates
uncertainty and conversion mistakes.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>