Replace bcopy() to update ether_addr

[Wojciech Puchar]

> but wonder whether the same does hold for MIPS/ARM. Getting it wrong
> there will lead to some very very poor performing code.
>
1) do - as already pointed out - standard copy of structure in C.
2) if compiler is found to generate bad code on some archs put assembly.

1 even if compiler is not smart is already far better than calling a 
function to copy 6 bytes that is plain stupid.