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

This reverts commit 7fd24ee9 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: I13b821522a44690a9afd45b1e73746fe49f4bffe
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>