hwmon: (acpi_power_meter) Fix compiler warning seen in some configura…

…tions

In some configurations, BUG() does not result in an endless loop but returns
to the caller. This results in the following compiler warning:

drivers/hwmon/acpi_power_meter.c: In function 'show_str':
drivers/hwmon/acpi_power_meter.c:380: warning: 'val' may be used uninitialized in this function

Fix the warning by setting val to an empty string after BUG().

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Robert Coulson <robert.coulson@ericsson.com>

drivers/hwmon/acpi_power_meter.c

@@ -391,6 +391,7 @@ static ssize_t show_str(struct device *dev,
 		break;
 	default:
 		BUG();
+		val = "";
 	}
 
 	return sprintf(buf, "%s\n", val);