Merge branch 'net-Get-rid-of-net_mutex-and-simplify-cleanup_list-queueing'

Kirill Tkhai says:

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net: Get rid of net_mutex and simplify cleanup_list queueing

[1/3] kills net_mutex and makes net_sem be taken for write instead.
      This is made to take less locks (1 instead of 2) for the time
      before all pernet_operations are converted.

[2-3/3] simplifies dead net cleanup queueing, and makes llist api
        be used for that.
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Signed-off-by: David S. Miller <davem@davemloft.net>