UPSTREAM: xfrm: rework default policy structure

[ Upstream commit b58b1f56 ]

This is a follow up of commit f8d858e6 ("xfrm: make user policy API
complete"). The goal is to align userland API to the internal structures.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 36d8cca5)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I65a493a79fbf4b42cc0c849748ff522ef0ed5568