thermal/drivers/tsens: Fix wrong check for tzd in irq handlers

Some devices can have some thermal sensors disabled from the
factory. The current two irq handler functions check all the sensor by
default and the check if the sensor was actually registered is
wrong. The tzd is actually never set if the registration fails hence
the IS_ERR check is wrong.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210907212543.20220-1-ansuelsmth@gmail.com