dma-mapping: Add header file for ARCH_DMA_MINALIGN

This is defined in the asm/cache.h header file. Update this header file to
include it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Adam Ford <aford173@gmail.com> #da850-evm
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 20b6d60..6a107d5 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -2,6 +2,7 @@
 #ifndef _LINUX_DMA_MAPPING_H
 #define _LINUX_DMA_MAPPING_H
 
+#include <asm/cache.h>
 #include <linux/dma-direction.h>
 #include <linux/types.h>
 #include <asm/dma-mapping.h>