Revert "netdevsim: rely on XFRM state direction instead of flags"

This reverts commit 08c30755 which is
commit 55e2f83a upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I3f26f3fb515286791fd97b6fc9c866e94e2395f6
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>