mtd: Add export.h for EXPORT_SYMBOL/THIS_MODULE where needed

These two common macros will be no longer present everywhere.
Call out the include needs of them explicitly where required.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/mtd/onenand/onenand_bbt.c

@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/onenand.h>
+#include <linux/export.h>
 
 /**
  * check_short_pattern - [GENERIC] check if a pattern is in the buffer