hwmon: (xdpe12284) Fix build warning seen if CONFIG_SENSORS_XDPE122_REGULATOR is disabled

0-day reports:

drivers/hwmon/pmbus/xdpe12284.c:127:36: warning:
	unused variable 'xdpe122_reg_desc'

This is seen if CONFIG_SENSORS_XDPE122_REGULATOR is not enabled.
Mark xdpe122_reg_desc as __maybe_unused to fix the problem.

Fixes: f53bfe4d ("hwmon: (xdpe12284) Add regulator support")
Reported-by: kernel test robot <lkp@intel.com>
Cc: Marcello Sylvester Bauer <sylv@sylv.io>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/xdpe12284.c

@@ -124,7 +124,7 @@ static int xdpe122_identify(struct i2c_client *client,
 	return 0;
 }
 
-static const struct regulator_desc xdpe122_reg_desc[] = {
+static const struct regulator_desc __maybe_unused xdpe122_reg_desc[] = {
 	PMBUS_REGULATOR("vout", 0),
 	PMBUS_REGULATOR("vout", 1),
 };