xfrm: remove xfrm_state_put_afinfo

commit 44abdc30
("xfrm: replace rwlock on xfrm_state_afinfo with rcu") made
xfrm_state_put_afinfo equivalent to rcu_read_unlock.

Use spatch to replace it with direct calls to rcu_read_unlock:

@@
struct xfrm_state_afinfo *a;
@@

-  xfrm_state_put_afinfo(a);
+  rcu_read_unlock();

old:
 text    data     bss     dec     hex filename
22570      72     424   23066    5a1a xfrm_state.o
 1612       0       0    1612     64c xfrm_output.o
new:
22554      72     424   23050    5a0a xfrm_state.o
 1596       0       0    1596     63c xfrm_output.o

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>