ethernet: use eth_hw_addr_set() for dev->addr_len cases

Convert all Ethernet drivers from memcpy(... dev->addr_len)
to eth_hw_addr_set():

  @@
  expression dev, np;
  @@
  - memcpy(dev->dev_addr, np, dev->addr_len)
  + eth_hw_addr_set(dev, np)

In theory addr_len may not be ETH_ALEN, but we don't expect
non-Ethernet devices to live under this directory, and only
the following cases of setting addr_len exist:
 - cxgb4 for mgmt device,
and the drivers which set it to ETH_ALEN: s2io, mlx4, vxge.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>