x86: move dma_sync_sg_for_device to common header

i386 gets an empty function.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/asm-x86/dma-mapping.h b/include/asm-x86/dma-mapping.h
index 1a301d7..53a404b 100644
--- a/include/asm-x86/dma-mapping.h
+++ b/include/asm-x86/dma-mapping.h
@@ -148,4 +148,15 @@
 		dma_ops->sync_sg_for_cpu(hwdev, sg, nelems, direction);
 	flush_write_buffers();
 }
+
+static inline void
+dma_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+		       int nelems, int direction)
+{
+	BUG_ON(!valid_dma_direction(direction));
+	if (dma_ops->sync_sg_for_device)
+		dma_ops->sync_sg_for_device(hwdev, sg, nelems, direction);
+
+	flush_write_buffers();
+}
 #endif