net: filter: fix warning on 32-bit arch

fix compiler warning on 32-bit architectures:

net/core/filter.c: In function '__sk_run_filter':
net/core/filter.c:540:22: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
net/core/filter.c:550:22: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
net/core/filter.c:560:22: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/filter.c

@@ -537,7 +537,7 @@ static unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *ins
 		 *   BPF_R0 - 8/16/32-bit skb data converted to cpu endianness
 		 */
 
-		ptr = load_pointer((struct sk_buff *) CTX, off, 4, &tmp);
+		ptr = load_pointer((struct sk_buff *) (unsigned long) CTX, off, 4, &tmp);
 		if (likely(ptr != NULL)) {
 			BPF_R0 = get_unaligned_be32(ptr);
 			CONT;
@@ -547,7 +547,7 @@ static unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *ins
 	LD_ABS_H: /* BPF_R0 = ntohs(*(u16 *) (skb->data + imm32)) */
 		off = IMM;
 load_half:
-		ptr = load_pointer((struct sk_buff *) CTX, off, 2, &tmp);
+		ptr = load_pointer((struct sk_buff *) (unsigned long) CTX, off, 2, &tmp);
 		if (likely(ptr != NULL)) {
 			BPF_R0 = get_unaligned_be16(ptr);
 			CONT;
@@ -557,7 +557,7 @@ static unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *ins
 	LD_ABS_B: /* BPF_R0 = *(u8 *) (skb->data + imm32) */
 		off = IMM;
 load_byte:
-		ptr = load_pointer((struct sk_buff *) CTX, off, 1, &tmp);
+		ptr = load_pointer((struct sk_buff *) (unsigned long) CTX, off, 1, &tmp);
 		if (likely(ptr != NULL)) {
 			BPF_R0 = *(u8 *)ptr;
 			CONT;