xfrm: store xfrm_mode directly, not its address

This structure is now only 4 bytes, so its more efficient
to cache a copy rather than its address.

No significant size difference in allmodconfig vmlinux.

With non-modular kernel that has all XFRM options enabled, this
series reduces vmlinux image size by ~11kb. All xfrm_mode
indirections are gone and all modes are built-in.

before (ipsec-next master):
    text      data      bss         dec   filename
21071494   7233140 11104324    39408958   vmlinux.master

after this series:
21066448   7226772 11104324    39397544   vmlinux.patched

With allmodconfig kernel, the size increase is only 362 bytes,
even all the xfrm config options removed in this series are
modular.

before:
    text      data     bss      dec   filename
15731286   6936912 4046908 26715106   vmlinux.master

after this series:
15731492   6937068  4046908  26715468 vmlinux

Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index 74d59e0..b61a8ff 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -135,7 +135,7 @@ static struct sk_buff *xfrm4_outer_mode_gso_segment(struct xfrm_state *x,
 						    struct sk_buff *skb,
 						    netdev_features_t features)
 {
-	switch (x->outer_mode->encap) {
+	switch (x->outer_mode.encap) {
 	case XFRM_MODE_TUNNEL:
 		return xfrm4_tunnel_gso_segment(x, skb, features);
 	case XFRM_MODE_TRANSPORT: