x86: move dma_cache_sync to common header

they are the same in both architectures.

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 b331a8d..51a79d7 100644
--- a/include/asm-x86/dma-mapping.h
+++ b/include/asm-x86/dma-mapping.h
@@ -185,4 +185,10 @@
 	dma_unmap_single(dev, addr, size, direction);
 }
 
+static inline void
+dma_cache_sync(struct device *dev, void *vaddr, size_t size,
+	enum dma_data_direction dir)
+{
+	flush_write_buffers();
+}
 #endif