UPSTREAM: xfrm: fix gro_cells leak when remove virtual xfrm interfaces

The device gro_cells has been initialized, it should be freed,
otherwise it will be leaked

Fixes: f203b76d78092faf2 ("xfrm: Add virtual xfrm interfaces")
Signed-off-by: Zhang Yu <zhangyu31@baidu.com>
Signed-off-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
(cherry picked from commit 4da402597c2b75c4b636ab2416baf921b363b325)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I6966b06be2095ee20663ab7b23082fd4516fe23f