twl-regulator: Add turnon delay to reg_enable

This change implements a basic turnon delay in the regulator enable function
to make it less probable that reg_enable returns before the regulator
output is at target level

Signed-off-by: Juha Keski-Saari <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Signed-off-by: Liam Girdwood <[e-mail]>

drivers/regulator/twl-regulator.c

···
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/err.h>
+#include <linux/delay.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
···
 {
 	struct twlreg_info	*info = rdev_get_drvdata(rdev);
 	int			grp;
+	int			ret;
 
 	grp = twlreg_read(info, TWL_MODULE_PM_RECEIVER, VREG_GRP);
 	if (grp < 0)
···
 	else
 		grp |= P1_GRP_6030;
 
-	return twlreg_write(info, TWL_MODULE_PM_RECEIVER, VREG_GRP, grp);
+	ret = twlreg_write(info, TWL_MODULE_PM_RECEIVER, VREG_GRP, grp);
+
+	udelay(info->delay);
+
+	return ret;
 }
 
 static int twlreg_disable(struct regulator_dev *rdev)