[iscsi] Fix minor typo in ibft_set_ipaddr()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/block/ibft.c

@@ -91,7 +91,7 @@ struct ibft_strings {
  * @v in		IPv4 address
  */
 static void ibft_set_ipaddr ( struct ibft_ipaddr *ipaddr, struct in_addr in ) {
-	memset ( ipaddr, 0, sizeof ( ipaddr ) );
+	memset ( ipaddr, 0, sizeof ( *ipaddr ) );
 	if ( in.s_addr ) {
 		ipaddr->in = in;
 		ipaddr->ones = 0xffff;