thermal: core: Fix memory leak in the error path

thermal: core: Fix memory leak in the error path

Fix the following error:

 smatch warnings:
 drivers/thermal/thermal_core.c:1020 __thermal_cooling_device_register() warn: possible memory leak of 'cdev'

by freeing the cdev when exiting the function in the error path.

Fixes: 584837618100 ("thermal/drivers/core: Use a char pointer for the cooling device name")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>