xfrm interface: ifname may be wrong in logs

xfrm interface: ifname may be wrong in logs

[ Upstream commit e0aaa332e6a97dae57ad59cdb19e21f83c3d081c ]

The ifname is copied when the interface is created, but is never updated
later. In fact, this property is used only in one error message, where the
netdevice pointer is available, thus let's use it.

Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>