[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/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b2b3053..f51f20e 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -659,7 +659,7 @@
 			break;
 		}
 		msf = kmalloc(optlen, GFP_KERNEL);
-		if (msf == 0) {
+		if (!msf) {
 			err = -ENOBUFS;
 			break;
 		}
@@ -816,7 +816,7 @@
 			break;
 		}
 		gsf = kmalloc(optlen,GFP_KERNEL);
-		if (gsf == 0) {
+		if (!gsf) {
 			err = -ENOBUFS;
 			break;
 		}
@@ -836,7 +836,7 @@
 		}
 		msize = IP_MSFILTER_SIZE(gsf->gf_numsrc);
 		msf = kmalloc(msize,GFP_KERNEL);
-		if (msf == 0) {
+		if (!msf) {
 			err = -ENOBUFS;
 			goto mc_msf_out;
 		}