We could use DEFINE_DMA_UNMAP_ADDR instead but using
CONFIG_NEED_DMA_MAP_STATE is a simpler way to see if a platform does
real DMA unmapping.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
  */
 static inline int need_skb_unmap(void)
 {
-       /*
-        * This structure is used to tell if the platfrom needs buffer
-        * unmapping by checking if DECLARE_PCI_UNMAP_ADDR defines anything.
-        */
-       struct dummy {
-               DECLARE_PCI_UNMAP_ADDR(addr);
-       };
-
-       return sizeof(struct dummy) != 0;
+#ifdef CONFIG_NEED_DMA_MAP_STATE
+       return 1;
+#else
+       return 0;
+#endif
 }
 
 /**