serial: sc16is7xx: add explicit return for some switch default cases

Allows to simplify code by removing the break statement in the default
switch/case in some functions.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20231221231823.2327894-12-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: hvilleneuvedoo

drivers/tty/serial/sc16is7xx.c

@@ -460,10 +460,8 @@ static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
 	case SC16IS7XX_IOCONTROL_REG:
 		return true;
 	default:
-		break;
+		return false;
 	}
-
-	return false;
 }
 
 static bool sc16is7xx_regmap_precious(struct device *dev, unsigned int reg)
@@ -472,10 +470,8 @@ static bool sc16is7xx_regmap_precious(struct device *dev, unsigned int reg)
 	case SC16IS7XX_RHR_REG:
 		return true;
 	default:
-		break;
+		return false;
 	}
-
-	return false;
 }
 
 static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg)