[CRYPTO] scatterwalk: Restore custom sg chaining for now

Unfortunately the generic chaining hasn't been ported to all architectures
yet, and notably not s390.  So this patch restores the chainging that we've
been using previously which does work everywhere.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 07b6f17..bd62431 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -52,6 +52,17 @@
 		cond_resched();
 }
 
+static inline void scatterwalk_sg_chain(struct scatterlist *sg1, int num,
+					struct scatterlist *sg2)
+{
+	sg_set_page(&sg1[num - 1], (void *)sg2, 0, 0);
+}
+
+static inline struct scatterlist *scatterwalk_sg_next(struct scatterlist *sg)
+{
+	return (++sg)->length ? sg : (void *)sg_page(sg);
+}
+
 static inline unsigned long scatterwalk_samebuf(struct scatter_walk *walk_in,
 						struct scatter_walk *walk_out)
 {