hwmon : (applesmc) Fix uninitialized variables warnings

Fix the following "maybe used uninitialized" warnings by
initializing the variables to keep the compiler quiet.
There is no "used uninitialized" in this case.

  CC [M]  drivers/hwmon/applesmc.o
drivers/hwmon/applesmc.c: In function ‘applesmc_init_smcreg’:
drivers/hwmon/applesmc.c:595:43: warning: ‘right_light_sensor’
may be used uninitialized in this function [-Wmaybe-uninitialized]
  s->num_light_sensors = left_light_sensor + right_light_sensor;
                                           ^
drivers/hwmon/applesmc.c:540:26: note: ‘right_light_sensor’ was
declared here
  bool left_light_sensor, right_light_sensor;
                          ^
drivers/hwmon/applesmc.c:595:43: warning: ‘left_light_sensor’ may
be used uninitialized in this function [-Wmaybe-uninitialized]
  s->num_light_sensors = left_light_sensor + right_light_sensor;
                                           ^
drivers/hwmon/applesmc.c:540:7: note: ‘left_light_sensor’ was
declared here
  bool left_light_sensor, right_light_sensor;
       ^

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>