thermal/drivers/qcom: Fix error code in adc_tm5_get_dt_channel_data()

thermal/drivers/qcom: Fix error code in adc_tm5_get_dt_channel_data()

Return -EINVAL when args is invalid instead of 'ret' which is set to
zero by a previous successful call to a function.

Fixes: ca66dca5eda6 ("thermal: qcom: add support for adc-tm5 PMIC thermal monitor")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210527092640.2070555-1-yangyingliang@huawei.com