[NET]: sparse warning fixes

Fix a bunch of sparse warnings. Mostly about 0 used as
NULL pointer, and shadowed variable declarations.
One notable case was that hash size should have been unsigned.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 8668ab3..cc8d4e2 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1407,7 +1407,7 @@
 	/* we assume size > sizeof(ra) here */
 	skb = sock_alloc_send_skb(sk, size + LL_RESERVED_SPACE(dev), 1, &err);
 
-	if (skb == 0)
+	if (!skb)
 		return NULL;
 
 	skb_reserve(skb, LL_RESERVED_SPACE(dev));
@@ -2144,7 +2144,7 @@
 	/* callers have the socket lock and a write lock on ipv6_sk_mc_lock,
 	 * so no other readers or writers of iml or its sflist
 	 */
-	if (iml->sflist == 0) {
+	if (!iml->sflist) {
 		/* any-source empty exclude case */
 		return ip6_mc_del_src(idev, &iml->addr, iml->sfmode, 0, NULL, 0);
 	}