regulator: wm831x-ldo - fix the logic to set REGULATOR_MODE_IDLE and REGULATOR_MODE_STANDBY modes

Problem description in current implementation:
When setting REGULATOR_MODE_IDLE mode, current implementation set
WM831X_LDO1_LP_MODE bit of ctrl_reg (which is wrong, it should clear the bit).
But due to a missing break statement for case REGULATOR_MODE_IDLE, the code
fall through to case REGULATOR_MODE_STANDBY and then clear
WM831X_LDO1_LP_MODE bit. So it still looks OK when checking the status
by wm831x_gp_ldo_get_mode().

When setting REGULATOR_MODE_STANDBY mode, it just does not work.
wm831x_gp_ldo_get_mode() will still return REGULATOR_MODE_IDLE because
the accordingly WM831X_LDO1_LP_MODE bit is clear.

Correct behavior should be:
Clear WM831X_LDO1_LP_MODE bit of ctrl_reg for REGULATOR_MODE_IDLE mode.
Set WM831X_LDO1_LP_MODE bit of ctrl_reg for REGULATOR_MODE_STANDBY mode.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

drivers/regulator/wm831x-ldo.c

@@ -215,8 +215,7 @@ static int wm831x_gp_ldo_set_mode(struct regulator_dev *rdev,
 
 	case REGULATOR_MODE_IDLE:
 		ret = wm831x_set_bits(wm831x, ctrl_reg,
-				      WM831X_LDO1_LP_MODE,
-				      WM831X_LDO1_LP_MODE);
+				      WM831X_LDO1_LP_MODE, 0);
 		if (ret < 0)
 			return ret;
 
@@ -225,10 +224,12 @@ static int wm831x_gp_ldo_set_mode(struct regulator_dev *rdev,
 				      WM831X_LDO1_ON_MODE);
 		if (ret < 0)
 			return ret;
+		break;
 
 	case REGULATOR_MODE_STANDBY:
 		ret = wm831x_set_bits(wm831x, ctrl_reg,
-				      WM831X_LDO1_LP_MODE, 0);
+				      WM831X_LDO1_LP_MODE,
+				      WM831X_LDO1_LP_MODE);
 		if (ret < 0)
 			return ret;