Merge branch 'xfrm: fixes for xfrm_state_find under preemption'

Sabrina Dubroca says:

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While looking at the pcpu_id changes, I found two issues that can
happen if we get preempted and the cpu_id changes. The second patch
takes care of both problems. The first patch also makes sure we don't
use state_ptrs uninitialized, which could currently happen. syzbot
seems to have hit this issue [1].

[1] https://syzkaller.appspot.com/bug?extid=7ed9d47e15e88581dc5b
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Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>