hwmon: (hwmon-vid) Add __maybe_unused attribute to dummy variable

This gets rid of this warning:

drivers/hwmon/hwmon-vid.c: In function 'get_via_model_d_vrm':
drivers/hwmon/hwmon-vid.c:249:27: warning: variable 'dummy' set but not used
[-Wunused-but-set-variable]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jean Delvare <khali@linux-fr.org>

drivers/hwmon/hwmon-vid.c

@@ -246,7 +246,7 @@ static struct vrm_model vrm_models[] = {
  */
 static u8 get_via_model_d_vrm(void)
 {
-	unsigned int vid, brand, dummy;
+	unsigned int vid, brand, __maybe_unused dummy;
 	static const char *brands[4] = {
 		"C7-M", "C7", "Eden", "C7-D"
 	};