blackfin: Add export.h to files using EXPORT_SYMBOL/THIS_MODULE

These particular files were just assuming that module.h was
somehow in the include paths.  Give them the more minimalist
header file explicitly.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/blackfin/kernel/dma-mapping.c b/arch/blackfin/kernel/dma-mapping.c
index 04ddcfe..f0d1118 100644
--- a/arch/blackfin/kernel/dma-mapping.c
+++ b/arch/blackfin/kernel/dma-mapping.c
@@ -12,6 +12,7 @@
 #include <linux/spinlock.h>
 #include <linux/dma-mapping.h>
 #include <linux/scatterlist.h>
+#include <linux/export.h>
 
 static spinlock_t dma_page_lock;
 static unsigned long *dma_page;