[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/unix/af_unix.c b/net/unix/af_unix.c
index 63a9239..eea7588 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2033,6 +2033,7 @@
 
 
 static void *unix_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(unix_table_lock)
 {
 	struct unix_iter_state *iter = seq->private;
 	spin_lock(&unix_table_lock);
@@ -2055,6 +2056,7 @@
 }
 
 static void unix_seq_stop(struct seq_file *seq, void *v)
+	__releases(unix_table_lock)
 {
 	spin_unlock(&unix_table_lock);
 }