regulator: da9052: Directly include of.h

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/drivers/regulator/da9052-regulator.c b/drivers/regulator/da9052-regulator.c
index 2678cbe..eaa91cc5 100644
--- a/drivers/regulator/da9052-regulator.c
+++ b/drivers/regulator/da9052-regulator.c
@@ -20,6 +20,7 @@
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 #ifdef CONFIG_OF
+#include <linux/of.h>
 #include <linux/regulator/of_regulator.h>
 #endif