thermal/core: Fix null pointer dereference in thermal_release()

If both dev_set_name() and device_register() failed, then null pointer
dereference occurs in thermal_release() which will use strncmp() to
compare the name.

So fix it by adding dev_set_name() return value check.

Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com>
Link: https://lore.kernel.org/r/20211015083230.67658-1-songyuanzheng@huawei.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>