dt: fix twl4030 for non-dt compile on x86

twl4030 still doesn't build correctly for x86 allmodconfig.  This
fix solves the missing symbol errors.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Benoit Cousson <b-cousson@ti.com>
diff --git a/drivers/mfd/twl-core.c b/drivers/mfd/twl-core.c
index 4970d43..54727ef 100644
--- a/drivers/mfd/twl-core.c
+++ b/drivers/mfd/twl-core.c
@@ -38,6 +38,7 @@
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/irq.h>
 #include <linux/irqdomain.h>
 
 #include <linux/regulator/machine.h>