etherdevice: Remove now unused compare_ether_addr_64bits

Move and invert the logic from the otherwise unused
compare_ether_addr_64bits to ether_addr_equal_64bits.

Neaten the logic in is_etherdev_addr.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>