net: add an identifier name for 'struct sock *'

Fix a warning from checkpatch:
function definition argument 'struct sock *' should also have an
identifier name in include/net/af_unix.h.
Signed-off-by: NBo YU <tsu.yubo@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/af_unix.h

@@ -13,7 +13,7 @@ void unix_notinflight(struct user_struct *user, struct file *fp);
 void unix_gc(void);
 void wait_for_unix_gc(void);
 struct sock *unix_get_socket(struct file *filp);
-struct sock *unix_peer_get(struct sock *);
+struct sock *unix_peer_get(struct sock *sk);
 
 #define UNIX_HASH_SIZE	256
 #define UNIX_HASH_BITS	8