netfilter: nf_nat_snmp_basic: fix a range check in NAT for SNMP

Fix a range check in netfilter IP NAT for SNMP to always use a big enough size
variable that the compiler won't moan about comparing it to ULONG_MAX/8 on a
64-bit platform.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/nf_nat_snmp_basic.c

@@ -439,8 +439,8 @@ static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
 				     unsigned int *len)
 {
 	unsigned long subid;
-	unsigned int  size;
 	unsigned long *optr;
+	size_t size;
 
 	size = eoc - ctx->pointer + 1;