[NET]: Add some acquires/releases sparse annotations.

Add __acquires() and __releases() annotations to suppress some sparse
warnings.

example of warnings :

net/ipv4/udp.c:1555:14: warning: context imbalance in 'udp_seq_start' - wrong
count at exit
net/ipv4/udp.c:1571:13: warning: context imbalance in 'udp_seq_stop' -
unexpected unlock

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 6bf876c..65f5ea4 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -211,6 +211,7 @@
 }
 
 static void xfrm_state_unlock_afinfo(struct xfrm_state_afinfo *afinfo)
+	__releases(xfrm_state_afinfo_lock)
 {
 	write_unlock_bh(&xfrm_state_afinfo_lock);
 }
@@ -1909,6 +1910,7 @@
 }
 
 static void xfrm_state_put_afinfo(struct xfrm_state_afinfo *afinfo)
+	__releases(xfrm_state_afinfo_lock)
 {
 	read_unlock(&xfrm_state_afinfo_lock);
 }