net: emaclite: Add support for little-endian platforms

Upcomming Microblaze is little endian that's why is necessary
to fix protocol and length loading.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: David S. Miller <davem@davemloft.net>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: netdev@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: devicetree-discuss@lists.ozlabs.org