[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/ipv4/fib_hash.c b/net/ipv4/fib_hash.c
index 9d54041..ee1ffdb 100644
--- a/net/ipv4/fib_hash.c
+++ b/net/ipv4/fib_hash.c
@@ -936,6 +936,7 @@
 }
 
 static void *fib_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(fib_hash_lock)
 {
 	void *v = NULL;
 
@@ -952,6 +953,7 @@
 }
 
 static void fib_seq_stop(struct seq_file *seq, void *v)
+	__releases(fib_hash_lock)
 {
 	read_unlock(&fib_hash_lock);
 }
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 2e5814a..88a059e 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -96,6 +96,7 @@
  * exclusive lock release). It should be ifdefed really.
  */
 void inet_listen_wlock(struct inet_hashinfo *hashinfo)
+	__acquires(hashinfo->lhash_lock)
 {
 	write_lock(&hashinfo->lhash_lock);
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 3532843..02fcccd 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1550,6 +1550,7 @@
 }
 
 static void *udp_seq_start(struct seq_file *seq, loff_t *pos)
+	__acquires(udp_hash_lock)
 {
 	read_lock(&udp_hash_lock);
 	return *pos ? udp_get_idx(seq, *pos-1) : (void *)1;
@@ -1569,6 +1570,7 @@
 }
 
 static void udp_seq_stop(struct seq_file *seq, void *v)
+	__releases(udp_hash_lock)
 {
 	read_unlock(&udp_hash_lock);
 }