xfrm: Fix xfrm_dev_state_add to fail for unsupported HW SA option

xfrm_dev_state_add function returns success for unsupported HW SA options.
Resulting the calling function to create SW SA without corrlating HW SA.
Desipte IPSec device offloading option was chosen.
These not supported HW SA options are hard coded within xfrm_dev_state_add
function.
SW backward compatibility will break if we add any of these option as old
HW will fail with new SW.

This patch changes the behaviour to return -EINVAL in case unsupported
option is chosen.
Notifying user application regarding failure and not breaking backward
compatibility for newly added HW SA options.
Signed-off-by: Yossef Efraim <yossefe@mellanox.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_device.c

@@ -67,7 +67,7 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
 
 	/* We don't yet support UDP encapsulation, TFC padding and ESN. */
 	if (x->encap || x->tfcpad || (x->props.flags & XFRM_STATE_ESN))
-		return 0;
+		return -EINVAL;
 
 	dev = dev_get_by_index(net, xuo->ifindex);
 	if (!dev) {