Merge branch 'ipv6_stable_privacy_address'

Hannes Frederic Sowa says:

====================
ipv6: RFC7217 stable privacy addresses implementation

this is an implementation of basic support for RFC7217 stable privacy
addresses. Please review and consider for net-next.

v2:
* Correct references to RFC 7212 -> RFC 7217 in documentation patch (thanks, Eric!)
====================

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