Attrib server should truncate attribute value to pdu length

When the size of attribute value is greater than pdu size, it should be
truncated to the pdu length - 2
diff --git a/attrib/att.c b/attrib/att.c
index 8655e5e..445b192 100644
--- a/attrib/att.c
+++ b/attrib/att.c
@@ -379,7 +379,7 @@
 uint16_t enc_read_by_type_resp(struct att_data_list *list, uint8_t *pdu, int len)
 {
 	uint8_t *ptr;
-	int i, w;
+	int i, w, l;
 
 	if (list == NULL)
 		return 0;
@@ -387,17 +387,16 @@
 	if (pdu == NULL)
 		return 0;
 
-	if (len < list->len + 2)
-		return 0;
+	l = MIN(len - 2, list->len);
 
 	pdu[0] = ATT_OP_READ_BY_TYPE_RESP;
-	pdu[1] = list->len;
+	pdu[1] = l;
 	ptr = &pdu[2];
 
-	for (i = 0, w = 2; i < list->num && w + list->len <= len; i++) {
-		memcpy(ptr, list->data[i], list->len);
-		ptr += list->len;
-		w += list->len;
+	for (i = 0, w = 2; i < list->num && w + l <= len; i++) {
+		memcpy(ptr, list->data[i], l);
+		ptr += l;
+		w += l;
 	}
 
 	return w;