bna: use ether_addr_copy instead of memcpy

Parameters of all ether_addr_copy instances were checked for proper
alignment. Alignment of bnad_bcast_addr is forced to 2 as the implicit
alignment is 1.
I have also renamed address parameter of bnad_set_mac_address() to addr.
The name mac_addr was a little bit confusing as the real parameter is
struct sockaddr *.

v2: added __aligned directive to bnad_bcast_addr, renamed parameter of
    bnad_set_mac_address() (thx joe@perches.com)

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>