regulator: axp20x: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warnings:

drivers/regulator/axp20x-regulator.c: In function ‘axp20x_set_dcdc_freq’:
drivers/regulator/axp20x-regulator.c:1023:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
   reg = AXP803_DCDC_FREQ_CTRL;
drivers/regulator/axp20x-regulator.c:1025:2: note: here
  case AXP806_ID:
  ^~~~
drivers/regulator/axp20x-regulator.c: In function ‘axp20x_set_dcdc_workmode’:
drivers/regulator/axp20x-regulator.c:1115:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
   reg = AXP806_DCDC_MODE_CTRL2;
drivers/regulator/axp20x-regulator.c:1121:2: note: here
  case AXP221_ID:
  ^~~~

Notice that in this particular case, I moved the whole comment
"Fall through to the check below.", which contains the "Fall through"
comment, at the bottom of the case, which is what GCC is expecting
to find.

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/axp20x-regulator.c

@@ -1021,7 +1021,7 @@ static int axp20x_set_dcdc_freq(struct platform_device *pdev, u32 dcdcfreq)
 		 * (See include/linux/mfd/axp20x.h)
 		 */
 		reg = AXP803_DCDC_FREQ_CTRL;
-		/* Fall through to the check below.*/
+		/* Fall through - to the check below.*/
 	case AXP806_ID:
 		/*
 		 * AXP806 also have DCDC work frequency setting register at a
@@ -1112,12 +1112,12 @@ static int axp20x_set_dcdc_workmode(struct regulator_dev *rdev, int id, u32 work
 		break;
 
 	case AXP806_ID:
-		reg = AXP806_DCDC_MODE_CTRL2;
 		/*
 		 * AXP806 DCDC regulator IDs have the same range as AXP22X.
-		 * Fall through to the check below.
 		 * (See include/linux/mfd/axp20x.h)
 		 */
+		reg = AXP806_DCDC_MODE_CTRL2;
+		 /* Fall through - to the check below. */
 	case AXP221_ID:
 	case AXP223_ID:
 	case AXP809_ID: