lib: dma-debug needs export.h for EXPORT_SYMBOL

There are no modular calls here, so just the minimal header for
the EXPORT_SYMBOL macro will suffice.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

lib/dma-debug.c

@@ -24,6 +24,7 @@
 #include <linux/spinlock.h>
 #include <linux/debugfs.h>
 #include <linux/uaccess.h>
+#include <linux/export.h>
 #include <linux/device.h>
 #include <linux/types.h>
 #include <linux/sched.h>