Merge branch 'net-ipv6-addr_gen_mode-fixes'

Sabrina Dubroca says:

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net/ipv6: addr_gen_mode fixes

This series fixes bugs in handling of the addr_gen_mode option, mainly
related to the sysctl. A minor netlink issue was also present in the
initial commit introducing the option on a per-netdevice basis.

v2: add patch 4, requested by David Ahern during review of v1
    add patch 5, missing documentation for the sysctl
    patches 1, 2, 3 are unchanged
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Signed-off-by: David S. Miller <davem@davemloft.net>