[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/core/sock.c b/net/core/sock.c
index 3804e7d..3d7757e 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2025,6 +2025,7 @@
 
 #ifdef CONFIG_PROC_FS
 static void *proto_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(proto_list_lock)
 {
 	read_lock(&proto_list_lock);
 	return seq_list_start_head(&proto_list, *pos);
@@ -2036,6 +2037,7 @@
 }
 
 static void proto_seq_stop(struct seq_file *seq, void *v)
+	__releases(proto_list_lock)
 {
 	read_unlock(&proto_list_lock);
 }