net:drivers/net: Miscellaneous conversions to ETH_ALEN

Convert the memset/memcpy uses of 6 to ETH_ALEN
where appropriate.

Also convert some struct definitions and u8 array
declarations of [6] to ETH_ALEN.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>