Thermal: Fix oops and unlocking in thermal_sys.c

This patch fixes the following mutex and NULL pointer
problems in thermal_sys.c:

 * mutex_unlock fix in update_temperature function
 * mutex_unlock fix in bind_cdev function
 * Correct early return to continue in bind_cdev function
 * NULL check fix in bind_cdev function
 * NULL check fix in bind_tz function

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>