regulator: as3722: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
by explicitly adding a fallthrough pseudo-keyword instead of letting the
code fall through to the next case.

Link: https://github.com/KSPP/linux/issues/115Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/c0efb81064f71837f19408f65b52d155103ee514.1605896059.git.gustavoars@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/as3722-regulator.c

@@ -455,7 +455,8 @@ static int as3722_sd_set_mode(struct regulator_dev *rdev,
 	switch (mode) {
 	case REGULATOR_MODE_FAST:
 		val = as3722_reg_lookup[id].mode_mask;
-	case REGULATOR_MODE_NORMAL: /* fall down */
+		fallthrough;
+	case REGULATOR_MODE_NORMAL:
 		break;
 	default:
 		return -EINVAL;