mfd: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required

These macros are in <linux/export.h> and will no longer be
implicitly everywhere anymore.  Fix it up in advance.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/mfd/twl6030-irq.c b/drivers/mfd/twl6030-irq.c
index eb3b5f8..b6bea42 100644
--- a/drivers/mfd/twl6030-irq.c
+++ b/drivers/mfd/twl6030-irq.c
@@ -32,6 +32,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/export.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/kthread.h>