[NET]: Forget the zero_it argument of sk_alloc()

Finally, the zero_it argument can be completely removed from
the callers and from the function prototype.

Besides, fix the checkpatch.pl warnings about using the
assignments inside if-s.

This patch is rather big, and it is a part of the previous one.
I splitted it wishing to make the patches more readable. Hope 
this particular split helped.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -927,7 +927,7 @@ static void sk_prot_free(struct proto *prot, struct sock *sk)
  *	@zero_it: if we should zero the newly allocated sock
  */
 struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
-		      struct proto *prot, int zero_it)
+		      struct proto *prot)
 {
 	struct sock *sk;