Merge branch 'dev_addr-const'

Jakub Kicinski says:

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net: constify netdev->dev_addr

Take care of a few stragglers and make netdev->dev_addr const.

netdev->dev_addr can be held on the address tree like any other
address now.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>