Remove magic numbers from Ethernet drivers and tests by defining
NET_ETH_MAX_DATAGRAM_SIZE and NET_ETH_MAX_FRAME_SIZE.
Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Any word started with underscore followed by and uppercase letter or a
second underscore is a reserved word according with C99.
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>